The museums of Old San Juan: the ones that are open are charming

Old San Juan, Puerto Rico, connected to modern San Juan by a bridge, is an islet with a past. Inhabited since 1521, it has a reputation for being rich in history. It has seven square blocks of thick-walled, arched, balconied, curvaceously plastered buildings with courtyards, narrow streets, and views of water in all directions, all strollable and freshly painted.

The area was valiantly brought back from seediness, starting in the 1950s. Walking the blue-cobbled streets and climbing the battlements of two brawny forts on opposite corners of Old San Juan, you get strong whiffs of spirit and culture.

History is harder to come by. Spanish colonial architecture presents a blank face to the street, with everything happening within.

In Old San Juan, a visitor is on the outside, clutching a copy of ''Que Pasa'' (the biweekly guidebook whose title means ''What's Happening'') and pushing on the fine arched doors of various museums. Most of them don't budge. ''Que pasa?'' indeed. No one, least of all the guidebooks, seems to know which museums are open. And the ones that are show you some interesting artifacts without labels or guides.

It wasn't always like this. Dr. Ricardo Alegria, who lobbied for protection of the historical buildings and did some of the restoration himself, was founding director of the Institute of Puerto Rican Culture. He established small , specialized museums in Old San Juan's houses, like the Museum of the Puerto Rican family and the Museum of the Indian. When he retired in 1978, his successor, Leticia de Rosario, closed them, intending to round up all the old books, furniture, and Indian artifacts in one big Museum of Puerto Rican Culture. But the big museum hasn't opened, and many small ones remain closed.

Meanwhile, de Rosario has resigned, and Angel Avila has been appointed the interim director. Mr. Avila says the Museum of Puerto Rican Culture will open in January or February in the Arsenal Building. This would be an easy walk from the cruise-ships dock, to the left behind the Coast Guard building. But observers call his plan ''optimistic,'' and even Mr. Avila, when interviewed, was unsure how long he will fill his post. Nonetheless, visitors should check at the tourist booth when they get off the boat.

A few doors swing open: Casa Blanca, built for Ponce de Leon in 1521 and lived in by his family for 250 years, is the oldest continuously inhabited residence in this hemisphere. It was restored after the United States Army finished using it as a fort in 1966.

White-walled rooms hold dark Spanish furniture, tapestries, needlework, and blue and white crockery, all from the 16th and 17th centuries. In one, two red brocade chairs are pulled up to a table. Long maces lean wickedly against a wall. There is a globe and a case of books, and trade winds still blow in through the leaves of a tamarind tree outside. The room speaks eloquently of oceanic plotting and imperialist squabbles.

The Pablo Casals Museum, near the former Dominican Convent, displays not only one of the Casals cellos but also his domino set and some of his scorecards. He played both excellently during the last 18 years of his life, which he spent here rather than in Franco's Spain.The museum has a library of videotapes of his performances, which attendants will play for you on request.

The San Juan Museum of Art and History had one room open in August. A few paintings leaned against the wall; two were labeled. A tantalizing case of Taino Indian relics of carved stone was only explained in Spanish. A contemporary show was being hung in another room. One can only hope they were getting ready for the winter season.

The Dominican Convent, home of the Institute of Puerto Rican Culture, had a contemporary print show I had to see at a jog before workmen took them down. The institute's Popular Arts Center, however, was open and doing a good trade in hand-sewn cloth dolls, wood carvings, and guitars.

The Casa del Libro, one of the first houses to be restored in the area, sits at the bay end of Calle Cristo, in a block of narrow, ornate town houses in cool , pale colors. The exhibit inside is slight, because the rare books in the collection can't be shown until a leaky roof is fixed. But the area looks as if it had always been a literary neighborhood. At the end of the street is a little chapel, and next to it, Parque de las Palomas is a little patch of green to look at New San Juan from (if you have a good attitude toward pigeons, whose park this is).

Just around the corner on Calle San Jose is The Bookstore. It's a good one for American and Hispanic literature. There are books on Puerto Rico, as well as daily newspapers from the United States.

The forts that sit on opposite corners of the old city like brawny shoulders are worth visiting if only because San Juan devoted itself to building them for 350 years.

San Cristobal Fort was started in 1633 to protect San Juan against land attacks after Sir Francis Drake and then the Dutch fought their way in by land. The guided tour turns this massive brick outcropping once again into a dreadful stationary war machine.

It collected its own water with a system of drains built into the cannon ramps, making it siege-proof. It had seven spare forts at its landward side which could be abandoned and then attacked as the enemy overran them. There were carefully graded tunnels to roll the 3,000- to 9,000-ton cannons from place to place, and a chapel to Santa Barbara, patron saint of artillerymen. The tunnels were rigged to be dynamited at any point if the enemy came up them.

Then there are places that give you such a distinct feeling for years gone by that if there were tour guides, books, and signs, you would ignore them. El Morro, just before dusk on a balmy evening, is one of those. The walling up of old San Juan started here in 1539. These walls are massive. They're faced with a mixture of lime, sandstone, and dirt, which is tawny, with yellow and pink chips. Their tops are as wide as roads, and peppered with sharp stones.

At El Morro, you feel the battle is over. It doesn't look cruel; it's a beautiful old husk in the light that bounces off the Atlantic. Inside, the triangular parade ground looks civilized in lemon yellow with white arches. A huge lawn sweeps up to it. Joggers and children run in the evening sun, and from the battlements you can look back at the patchwork of colored stucco, much of it repainted in the last 30 years, that covers the hills of Old San Juan like a gay mosaic.

Turn around and see how the fort cuts into the ocean like a prow. The wind blows the way it blew when it blew the Spaniards here in 1493. Palm trees rattle. You suddenly see a cruise ship standing on the sea like a building, and imagine how the smaller and deadlier invading ships of Sir Francis Drake, the Count of Cumberland, and the Dutch must have just sprung up on the horizon. Looking into the ocean, one can still manage a shudder at what it must have meant to come here when this was still the New World. Practical information

The Gran Hotel El Convento, Calle Cristo 100, is in the middle of Old San Juan, by location and historically. In 1646 it became a Carmelite convent. When the convent was closed in 1909, the city bought it. It was about to be torn down when Dr. Alegria had it declared a historical landmark. Subsequently, it was bought by a member of the Woolworth family and turned into a hotel. Now run by Provincial de Hoteles de Mexico, it is newly refurbished, with glass doors at the tall shuttered windows to keep out the heat. Rooms are from $75 single to $ 150 for a super deluxe double. Some have stained-glass windows and their own terraces.

The Ballet Folklorico of Puerto Rico performs Jan. 19 - Feb. 15 at the Tapia Theater, a restored gem with dashing red and black striped seats.

La Bombonera Puig y Abraham, an unprepossessing soda fountain and bakery on Calle San Francisco near the corner of Calle Tanca, makes superb chocolate ice cream sodas.