The heart dances to a different beat way out west in western Puerto Rico.

Far from the spinning roulette wheels and the skyscrapers of San Juan, out where the vaqueros ride through the fields of tall cane, lives a land of pocket-sized colonial villages, king-size strands of sand four miles long, surfing beaches known only to big board-riders and a deserted island still inhabited by weird lizards left over from pre-history.

Western Puerto Rico is well known to islanders and even to business men from the mainland with interests in Ponce and especially in Mayaguex. But to most migrants who come from the mainland it remains a tourist secret.

Take San German, which advertises itself on the highway where a side road leads to its limits as the "Ciudad de las Lomas." It is the city of the hills, built on the heights where it would be safe from the Indians and from the pirates. It is the second oldest settlement in Puerto Rico.

The local church, with its white columns and trompe l'oeil ceilings and crystal chandeliers, commands the loftiest hill. Here one can stand at the portal and survey the plaza. At the far end looms the city hall, hung with a large sign which says, "Happy Hills -- 50th Anniversary."

What is "Happy Hills"? I ask a Puerto Rican friend, and he explains that it is a local orchestra. Is it not strange that such a message of felicitation should adorn a public building? "That's nothing," he assures me. "In the town of Cabo Rojo, the mayor is the leader of the local orchestra and his three sons play in the band."

Beyond stands the aging, burnished facade of Porta Coeli, a chapel on a knoll at the end of San German plaza. It may well have been there at least since the end of the 17th century. Some historians claim it predates Jamestown. Now it is a museum of religious art and is undergoing restoration by the Institute of Puerto Rican Culture.

Although the untutored visitor might miss its entrance if he sneezed while passing it, the oasis in San German is the quintessence of a hideaway hotel. It inhabits a 200-year-old building, is equipped with a San German chef who worked at New York's Waldorf-Astoria, and will put you up in a double room with private bath for $22.05.

On the other hand, in Mayaguez, on the west coast, the Mayaguez Hilton is a splendid preserve of 150 rooms crowning a hilltop and surrounded by 25 acrs of tropical foliage. Well known to businessmen, it is all but overlooked by tourists and it often has rooms available when the rest of the Caribbean is packed.

Two hundred kinds of trees and flowers, a part of the land used by the Institute of Tropical Architecture, give it a stunning park. But it also has an Olympic pool, a poolside bar and three tennis courts.

Best of all, its young Bavarian chef, Dieter Hannig, is a culinary artist of international class whose master works appear in the Rotisserie Room and in the snack bar at the pool. Deep in his kitchen domain, Hannig has created his own den, a rustic corner called the Chef's Table. In this secret corner, Hannig serves a nine-course epicurean dinner that would knock the toques off visiting chefs from the three-star restaurants of France. kA fantasy of presentation and finesse, the Chef's Table can be booked by a minimum of four and a maximum of six. At $50 a head, wines included, reservations are hard to come by.

The arrival of this country hotel in 1964 has made Mayaguez the honeymoon capital of Puerto Rico. And its rates, at about $40 a night, with no seasonal increases when the chill winds blow in the north, stand like a relic of old times.

The joys of Mayaguez are simple enough. One can sit in the square of the handsome Plaza de Colon and admire the travertine walks, the lighted fountain, the bronze statues holding globes and the fringe of laurel of India trees.

It is perhaps 40 minutes to the serenity of Boqueron, a cove lined with four miles of sand. Bungalows strung along the beach with four bunk beds in one room and a double bed in the other rent for $25 for three days. The pad comes with stove, refrigerator, toilet and shower, but you must bring your own bedding and cookware.

For day-trippers, Boqueron has lockers and a cafeteria. But no visitor who has come this far should miss the neighborhood seafood restaurants. At the Caribe, just outside the village, one can sit under a print of The Last Supper and work on lobster stewed in wine at $8, the most expensive item on the menu. On the harbor, where herons come for dinner, too, restaurants like Ruicof are set on pilings that lead from the mangrove flats. Here the fare will be octopus stew or conch, turtle steaks and lobster diablo. hThe check will run to $10 -- for two.

Surf as large as the combes of Hawaii roll to shore at Ricon, half an hour north of Mayaguez. The surf's up from now until mid-May at places called Dogman (for a hermit who lives there and keeps cannies), Overnights (for the beach sleepers in from San Jan) and Gas Chambers (for the tunnelled waves).

To get way out of this world, a departurist can take a boat (rough) or a plane (easier) for Mona Island, a slab of limestone halfway to the Dominican Republic. In Mona's caves Taino Indians left their hieroglyphics. Wild pigs, goats and iguanas four feet long live in contentment. So does a platoon of the police who lie in wait for the pot runners. They've found Western Puerto Rico, too.