Antigua; The rates have just dropped 30 to 40 percent on this easily accessible island

If Antigua had nothing else to recommend it but its beaches, it could still stand up to any island in the West Indies. But it has much more: a historic and architectural jewel called Nelson's Dockyard, constant cooling breezes that make air conditioning irrelevant, a port town with all the color and rhythms Harry Belafonte used to invoke, and a different hotel for every taste and almost every budget.

Antigua (pronounced An-tee'-ga) sounds even more appealing now that the high-season rates have made their annual spring descent of 30 to 40 percent. Make no mistake, the Dec. 15-April 14 figures can be steep, and yet during a week in early February I found the poshest hotels totally booked and the more economical spots wanting for business, proving once again that hard times never keep the wealthy at home.

Antigua lies about a third of the way down the long, arcing Caribbean chain in the neighborhood of Nevis, St. Kitts, St. Barts, and Saba. Together with her little sister, Barbuda, the island gained its independence on Nov. 1, 1981, but the ties to Mother Britain are still apparent. There is English marmalade on the shelves, kippers on the breakfast menus, and autos on the left side of the roads.

For a small, remote, and not highly celebrated island, Antigua is a surprisingly easy mark from the United States. American Airlines had me there in three hours, thirty minutes nonstop from Kennedy International Airport, using a little 108-seat 727, as if we were merely popping down to Atlanta.

Even before the descent into Coolidge International Airport, you can make out the beaches - one sandy cove after another in all shades from talcum to gold. Visible too is the muted green landscape, dun-colored at the edges, not particularly mountainous in the interior, with long-disused stone sugar mills scattered about. What you can't see from above are the holes in the roads, deeper and more numerous than Manhattan's in March, and perhaps one reason why Antigua tourists don't venture much beyond their own hotel beach.

This was decidedly the case at the Half Moon Bay hotel, where I spent the first half of my Antiguan week. Half Moon, probably the second-plushest hotel on the island next to Curtain Bluff, has a nine-hole golf course and a batch of tennis courts in nice landscaping, but the perfect, curving three-quarter-mile beach was really all the 200-odd guests seemed to need. Sometimes for variety they hiked around the bend, following a marked trail along a dramatic headland in one direction, or climbing over coral boulders to the private Mill Reef Club beach in the other.

For a day or two I was content to stay put, to share my terrace with the iridescent green hummingbirds and the darting little yellow banana quits, to walk up the beach and admire the architecture of the visitor from Regina, Saskatchewan, who each day built a different-model edifice in the sand - a Gothic church complete with a tiny stained-glass rose window, a Welsh castle patterned after Caernarvon. Then one morning I found myself bouncing down the road - the leftm side, I kept reminding myself - in a rented car bound for English Harbour.

At the busiest corner of the large and meandering harbor, a sort of Caribbean Williamsburg called Nelson's Dockyard, is well on its way to completion. Once I had soaked up the 1790s of Horatio Nelson, had lunch on the terrace of the historic Admiral's Inn, and admired the lovely lineup of international yachts (hailing from Malta to Toronto), it was time to go beach hunting again.

Antigua is said to have a different beach for every day of the year, and while this may be slight hyperbole, everyone you meet does seem to have a different favorite. The manager of the Admiral's Inn said she favored Galley Bay , but I chose one closer by, Curtain Bluff, recommended by the young man who filled my gas tank in English Harbour.

The road to Curtain Bluff was a 20-minute tropical adventure. I passed through the villages of Liberta and Sweet's and in the latter narrowly averted (as they say) a mishap when a man lost control of his donkey in my path. Then it was up and over Fig Tree Hill on a narrow winding road, through one of the greenest and most jungly swatches of the island, and down to Curtain Bluff.

Never mind the hotels posted at either end of the beach (the esteemed and expensive Curtain Bluff and the comfortable little Callaloo), the warm, golden shoreline was empty. Far to the left, the sea crashed and foamed about a jagged cliff, to the right an ancient stone mill stood guard on a green bluff, and directly before me lapped a friendly surf.

In midweek I moved across the island to an entirely different milieu on Dickenson Bay, near the town of St. John's. Now instead of the pampering Modified American Plan of Half Moon Bay, there was the fetch-your-own-meals style of the 10-room Siboney Beach Hotel. But all the comforts were there - bedroom, sunny living room, kitchen, and treetop terrace. Siboney Beach is one of Antigua's better bargains ($60 a day after April 15).

Everything was closer at hand now. St. John's, a few miles south, proved far more appealing than I had been led to believe, with its brightly painted frame buildings, shaded outdoor cafes, and lively market: kerchiefed and straw-hatted women selling piles of fat carrots, spiny christophine, squashes the size of baseball bats, and shavings from the maubey tree. (''Boil it, put in some sugar, and it makes a very nice drink,'' I was advised.)

As always there were more beaches, and none better than the one stretching before the Galley Bay Hotel south of town. Galley Bay, with only 30 rooms, some of them so-called Gauguin units, i.e., thatched cottages, has a feel of the South Pacific about it. Had I closed my eyes I could have been in Bora-Bora. But I kept them open. Galley Bay, in fact, Antigua itself, can stand on its own. TPractical information:

Contact the government of Antigua and Barbuda department of tourism for further details: 610 Fifth Avenue, Suite 311, N.Y. 10020.

American Airlines has a number of tour packages designed to bring down the overall cost of visiting Antigua. Pan American has begun service to the island, from New York and Miami, and BWIA also flies into Coolidge International.