Midwinter dreams of tropical sunsets and vanilla beaches are too often just that: dreams. In years past the reality was that a vacation in a warm place between December and April was something only a tycoon or a rock star could afford. This is not to be in 1983, however - at least not in Mexico or in the French West Indies, where the dollar is suddenly buying an affordable place in the sun.
When Mexico devalued the peso on Dec. 20, the third or fourth such move in the last year, one could almost feel the sands of Puerto Vallarta and the Mayan ruins of Chichen Itza drawing closer. Along the corridors of Madison Avenue someone was surely ready to uncork the old slogan, ''You can't afford notm to go.''
The latest devaluation set the peso at about 150 to the dollar, or nearly six times what it was a year ago. But even in the days before this 50 percent devaluation, when the peso was fetching 70 to the dollar, travelers were coming back from Mexico with can-you-top-this tales of bargain-basement touring. ''I had to write 'em down,'' said a friend, reeling off some sample prices, ''so no one would doubt me. In Mexico City a subway ride was a penny and a half. A glove-leather garment bag cost me $90. On Fifth Avenue it would have been $600. A hand-carved leaded-glass cabinet was $11. Dinner in a Mexican family-style restaurant cost $3. A taxi from the airport to Mexico City was down from $15 to
While rooms in comfortable Mexican hotels are as low as $12 to $14 a night, even the most deluxe lodging is within reach. My economizing friend stayed at the posh Hacienda Cocoyoc near Cuernavaca for $75 a night. That may sound steep, but this stateliest of country houses, where, he said, ''Montezuma used to hang out,'' is full of gardens, fountains and private swimming pools, and all the rooms are master suites.
Curious to know if Mexico-bound planes were filling up and what sort of new packages were being dangled, I phoned a specialist in the field, Alexander Charters and Tours of 2607 Nostrand Avenue, Brooklyn. Vida Kurtin, head of Alexander's Mexico desk, said the big bargains from the East Coast are to the Mexican Caribbean - namely the Yucatan Peninsula and the resorts of Cozumel and Cancun. She said prices are running 20 to 45 percent lower than last winter.
She dangled this January offer: a week in either Cozumel or Cancun for $399 per person (double occupancy) in a beachfront hotel. A year ago the same package - air fare with United, hotel room, airport transfers, and tips included - cost Chichen Itza and Tulum. On an Alexander tour, the side trip cost $100 for two in 1982 but only $52 this year - or $59 including lunch. Whatever the state of the peso, Cozumel is a magnet for scuba divers because of the legendary Palancar Reef. The glossier Cancun will satisfy snorkelers.
Although the dollar has slipped slightly in relation to the French franc, the overseas departments of Guadeloupe and Martinique are still among the better bargains in the Caribbean. The exchange rate in late December was almost 7 francs to the dollar, two higher than a year ago. As a cautionary tactic, you should consider buying your francs in the United States. The last time I was in the French islands, I didn't get the rate quoted in Paris and was never told just why. Inquire, too, as to whether buying francs in advance will help you in St. Martin or St. Barts, two other French outposts in the West Indies. The dollar is used so widely on both islands that the franc may do you little good.
Guadeloupe can be done economically even when the franc is strong, but it takes a special effort. Haute cuisine redolent of the homeland can be found all over the island, but the spicy and unpricey way to eat is Creole. One of Guadeloupe's best Creole restaurants, a minor landmark, is La Chaubette, a breezy little roadside cafe with madras curtains and matching tablecloths.
Madame Gitane Chevalin, the proprietress, who has a smile of gold, may urge you to start with an order of accras, hot Creole fritters, and proceed through the following sequence: crabes farcis, peppery stuffed crabshells; palourde au sauce, clams in garlic and parsley saucem, and finally a main course of turtle steak grilled in a sauce piquant with onions and a side dish of pureed christophene, a West Indian squash. If you can resist Madame Chevalin and eat less bounteously, the check will be under $10.
Another reasonably priced Creole fixture is Karakoli, which lies secreted in a grove of palms and sea grapes just off a long crescent beach called Plage de la Grande Anse on the less busy Basse Terre side of the island. You can come straight off the beach - one of the finest I've combed in the Caribbean - and sit down to lunch on the terrace in your bathing suit.
If you pass up the stylish resort strips of Gosier and St. Francois, lodging on Guadeloupe can be an inexpensive proposition. The mountainside inn, Relais de la Grande Soufriere - also the site of a hotel school and a splendid restaurant - charges just 250 francs (about $35) for two including continental breakfast, tax, and service. And down on the beach at Ste. Anne, the 10-room Auberge du Grande Large costs 280 francs a day withoutm tax or service. Any way you figure it, Guadeloupe is more than just a dream this winter. And Mexico is a mirage come true.