Island drives rarely require navigation: Keep the beach on the same side of the car and you’ll eventually end up back where you started. Except on Puerto Rico. Here, the most scenic and fascinating road—actually a network of roads—runs not along the island’s often-crowded sandy outline, but down its empty, mountainous middle, straight across the Cordillera Central, the spine of what may be the most varied, most colorful, most cosmopolitan, and yet most oddly remote and foreign of all the islands in the Caribbean.

Did I say straight across the spine? Silly me. I’ve never driven a more convoluted course than the one followed by Puerto Rico’s rural Ruta Panorámica. To find our way along this route, with a brief diversion to coastal Ponce, it took not one but two navigators (both of us aviators accustomed to maps, charts, compasses, and dead reckoning). Our flight path: a 100-mile long subtropical land spiderwebbed with roads that at best are confusingly signposted and at worst have no signs at all. They run the gamut from superhighways where exits are simply marked salida—salida to where, I beg to ask—to crude blacktops into the island’s back of beyond, so narrow and tortuous that a strong bicyclist could have beaten our Volvo Cross Country, the SUV-challenging all-wheel-drive station wagon in which we explored the Puerto Rico that lies far from San Juan and its vanilla-white resort hotels.

Day 1: 137 Miles —San Juan to Rincón

Twenty years ago, I went to Puerto Rico to write the script for a film about the Arecibo radio-astronomy observatory (no, not Jodie Foster’s Contact but an unremembered documentary). The “telescope”—an enormous metal-mesh bucket that not only collects radio waves from outer space but beams radar signals back out—is a 1,000-foot-diameter bowl built into a limestone sinkhole amid the low, karst-dotted, jungly landscape about ten miles south of the otherwise undistinguished city of Arecibo.

When I first visited the observatory, the road was a remote, partially unpaved challenge and the radio telescope a lonely scientific outpost. Today, the road is rife with settlements, stores, and houses, and at the end of it there’s a visitors center, a crowded all-about-astronomy clutter with a viewing platform that looks down into the enormous bowl. They flipped the switch on the dish in 1964, and it’s showing its age. The support towers are streaked with rust, and the metal mesh is dark with corrosion and grime, but it’s a you’ve-never-seen-anything-like-it sight, and since large optical telescopes are generally atop remote mountain peaks, this is about the most accessible major astronomy site you’ll ever find.

On the other hand, finding the Horned Dorset Primavera, Puerto Rico’s classiest small resort, was a little more difficult. My co-driver and I left the main road, Route 2, and headed for the coast south of Rincón on what looked on the map like a splendidly direct back road. Big mistake. The cement truck behind which we soon found ourselves groaned up and down the impossibly steep hills at walking speed. The Horned Dorset turned out to be hiding behind a narrow gateway and a bronze Relais & Châteaux plaque, that unfailing testament to a lodging’s grace, style, uniqueness, and luxury. Didn’t fail us this time, either. The resort’s only permanent guest, the house macaw Pompideau mutters, “Hola, hola,” as he buries his head under his cage’s newspaper flooring, as though embarrassed to do tricks on demand. In fact, he has no shame. Don’t macaws live to be 70 or 80 years old, we ask? “This one? Not likely with his diet,” the bartender says with a laugh. So the guests all feed him rich food? “No, he loves Jack Daniel’s.” Pompideau gets so sloshed, in fact, that we later see him scramble to the top of his man-size cage only to let go, falling leadenly to the bottom. Not to worry, the bartender tells us: The bird’s driver’s license has already been revoked.

Day 2: 118 Miles —Rincón to Ponce via the Ruta Panorámica

Puerto Rico’s Ruta Panorámica, which stretches more than 120 miles from Mayaguez to Yabucoa, is simply a labyrinth of lane-and-a-half back roads with unmarked intersections, constant blind hairpins, locals doing 15 miles per hour in ’70s Chevys, wild dogs fornicating in the middle of the road, and occasional Ruta Panorámica signposts that appear more as rewards than directions. Don’t try this without an enormously detailed road map of the sort you’ll find only on the island, not in a mainland travel shop.

Another tip: Start at the southeast end of the route, in Yabucoa, which is better marked, rather than in Mayaguez, on the west coast, where it took us an hour of aimlessly Volvoing around to find somebody who’d even heard of the Ruta Panorámica.

The good news is that once you find it, the road is not only panoramic but also quite an adventure. The welter of tiny roads along the Cordillera Central climbs into Puerto Rico’s cool, high interior, a jungly countryside with vistas of sheer cliffs and the sea below. These are, after all, the highest U.S. mountains east of the Rockies. Anybody who goes to Puerto Rico expecting a floating Florida, a tropical almost-state, is in for a big surprise. Outside the major resort areas, it’s todo Español, including on all the highway signs. Since we grabbed the island from Spain in 1898, colonialists have blustered that Puerto Ricans should damn well learn to speak English. Forget about English—a lot of Puerto Ricans think theirs should be an independent country, and they have a point.

The Ruta Panorámica follows what must once have been farm trails and cart tracks, and the Volvo’s steering gets cranked from lock to lock along an endless series of hairpins. Here and there, the road is littered with fallen oranges, and banana trees are heavy with hands of the green fruit. Flamboyants and impatiens grow everywhere along the jungly roadside, although we’re periodically jerked back to urban reality by the forests of fancy microwave and transmission towers that sprout from the higher peaks.

Past Adjuntas, about a third of the way along the Ruta Panorámica, we decide to return to civilization for the afternoon and turn off down twisty, narrow Route 10 to the colorful old south-coast city of Ponce. (There’s also a new superhighway just across the valley, if you prefer cruise control to cornering.)

Ponce is obviously prosperous: We see three Porsche 911s and a $120,000 Mercedes-Benz SL600 in an hour. “What do you people do with fast cars on this road-challenged island?” I’ll later ask a Maserati Biturbo owner whom we meet in San Juan. “Most of us try the San Juan–Ponce run very early in the morning and see if we can do it in under an hour,” he says, laughing. San Juan to Ponce via Route 52, the autopista, is only 64 miles, but it’s laced with radar traps. “Actually, there are four times of day when you can drive as fast as you want and never get a ticket,” he adds. “Morning coffee, lunch, afternoon coffee, and dinner.”

It’s Friday night and the Holiday Inn’s casino is jammed. It takes me just a moment to realize that I’m the only non–Puerto Rican, and certainly the only nongambler, in the place. The giddy local crowd is utterly unlike the mournful gaming tourists I witnessed feeding the slots in San Juan. The music, live and loud, is as much a part of the gaiety as are the craps and blackjack tables. A middle-aged woman comes out of the crowd to sing, covering her face in embarrassment and shushing her clapping friends as she stands by the keyboard. When she breaks into song, her voice is strong and pure, and it sounds as though she’s been doing this all her life. San Juan suddenly seems a lot more than 64 miles away.

Day 3: 150 Miles: —Ponce to the southeast coast

The Maserati’s favorite highway, Route 52, becomes our road east. Climbing away from the sea and into the lush, green mountains, it briefly feels like an interstate heading into the foothills of the Rockies. Our radar detector braaaps, and a Honda Accord zips past us at 70 (the speed limit here is 55) with the snout of a big highway-patrol Crown Vic half a car length behind. For a mile or so, the Accord driver cruises in the passing lane, utterly oblivious, until the cop pulls to his right and waves him over.

Drivers, tangled in the island’s urban and small-town traffic, are surprisingly amiable. They have to be. Puerto Rico is saturated with cars and trucks, there are few stop lights and virtually no stop signs amid the narrow and mazelike streets, drivers stop in the middle of the road to chat, and parking is absolutely free-form. The only way traffic moves at all is through an entirely voluntary system of after-you gestures—or the reverse, “’Scuse me, but look out, here I come!”

At Cayey, we rejoin the Ruta Panorámica for a side trip to the mountain town of Aibonito, known, for no discernible reason, as “the Switzerland of Puerto Rico.” (Is there an Aibonito of Switzerland?) Maybe it’s the weather: One of Aibonito’s main claims to fame is that the temperature dropped to 40 degrees here one day in 1911, which must have been a stunner on an island where in December, my glasses fog every time I walk out of an air-conditioned building.

The southeast coast is a scatter of small resorts that are quite the opposite of the north-coast monoliths flanking San Juan. Puerto Ricans come here to lie all day in beachfront hammocks and laze on small scimitars of sand, where the most exciting activity is not renting Jet Skis but swinging out over the surf on a time-worn trapeze that somebody shinnied up a palm trunk to install.

Day 4: 115 Miles —The southeast coast to San Juan

If you do nothing else in Puerto Rico, go to El Yunque—officially the Caribbean National Forest. Barely 45 minutes east of San Juan, this spectacular mountain rain forest must be the most accessible of all our National Park System’s wilderness areas, yet it also seems to be one of the least trafficked. Hiking half an hour to one of the forest’s magnificent high points on a sunny Sunday, we pass three or four other groups and find six people at the Mount Britton scenic overlook tower, where the view easily stretches 50 miles, from San Juan’s resort row in the west to the islands of Vieques and Culebra in the east. The hikers on the steep trails range from full-Patagonia-technical backpackers to families—Grandma doing just fine, Dad in his shiny going-to-church pants and slick shoes, overweight Mom tugging the 18-month-old along.

El Yunque is far more than a jungle for tourists. There are four specific and different kinds of protected rain forest amid its 28,000 acres—tiny for a national park—and even a mere four hours invested in driving to and hiking it will take you past great fernlike trees, strange palms, orchids, vivid parasite plants latched onto host trunks, Yosemite-like cliffs soaring hundreds of feet but covered with jungly thatch, and perhaps even a rare bird or animal. Our score: one feral cat—locals come to El Yunque to ditch their pets—and the sound of a coquí, the tiny tree frog that constantly speaks its name. The big attraction is the almost extinct Puerto Rican parrot. About 40 live in the forest. They might see you, but you won’t see them.

Route 187 back to San Juan is the lazy seaside alternative to busy Highway 3. Much of the road runs along the beaches used by San Juaneros fenced out of the expensive resort strands. Both sides of the two-lane are lined with parked cars and stands selling everything from piña coladas to piononos (deep-fried cones of battered, mashed plantains stuffed with ground meat). There are carts dispensing piraguas (snow cones) and shacks cooking up empanadillas (fried dough pockets filled with you-name-it meats and fish), and with the Volvo’s windows and sunroof wide open, the air is redolent of cooking oil, cocoa butter, and fishy beach scents.

Isla del Encanta, Puerto Rico’s license plate boasts—“Isle of Enchantment.” Not everywhere and always, of course, but certainly here and now.

Pit Stops

HORNED DORSET PRIMAVERA This small (31 rooms), utterly charming seaside inn on the west coast, in Rincón, is everything that San Juan’s huge, impersonal resort hotels are not. It’s stylish, tasteful, intimate, beautifully sited, and impeccably staffed. The food is superb, the suites are elegant, and the cluster of Mediterranean-style buildings sprawls discreetly along the resort’s own splendid beach (800-633-1857; www.horneddorset.com; doubles, $280–$650; no children under 12).

CARIBE PLAYA BEACH RESORT At the other end of the island is this unpretentious beachfront complex near Maunabo. You’ll share its 32 simple rooms not with Hawaiian-shirted mainlanders but with vacationing Puerto Ricans. Hammocks, beach chairs, and a pleasant pool are as fancy as it gets, but the beach is delightful, unspoiled, and about five feet away. Eat at the simple restaurant or pick up provisions at the supermercado and grill your own on the barbecue (787-839-6339; www.caribeplaya.com; doubles, $79–$104).

GALLERY INN If you’re shocked by the concept of an inn where they clean the “lobby” with a garden hose—a dozen uncaged parrots and cockatoos with the run of the place do make a mess—avoid this seven-level hodgepodge in Old San Juan. If you’re intrigued by being welcomed into a combination art gallery, sculptor’s studio, zoo, museum, out-of-control greenhouse (“Feed me, Seymour . . .”), and what must once have been a fancy bordello, go straight to San Juan’s most unusual accommodations. Trust me, you’ll be fascinated (787-722-1808; www.thegalleryinn.com; doubles, $145–$350).