Mexico City — The lobby of the top-ranked Camino Real Hotel here sweeps you past fountains and over plush carpets to rooms overlooking gardens and pools. Its flagship restaurant, Fouquet's de Paris, provides every woman with a long-stem rose and apparently employs waiters by the battalion.
And don't worry about the cost: A large double room may go for $9,000 per night, with dinner for two at perhaps $4,500.
Which, of course, could make your hair stand on end. Until you remember that in Mexico the ''$'' sign stands for pesos, and the peso is trading at about 150 to the dollar. That brings the room to about $60 US, with dinner for half as much.
And that makes Mexico one of the tourist bargains of the decade - a phenomenon that leaves the financially battered Mexican government, desperate for foreign currency, happy that at least one feature of its economy is surging ahead.
A report on tourism recently released by the Bank of Mexico says that foreign visitors (most of whom are from the United States and Canada) should provide a net income of 750 million tourist-related dollars to the nation in 1983.
The president of the country's Confederation of Chambers of Commerce, Emilio Goicoechea Luna, is even more optimistic. ''In tourism, we can find the saving formulas amid economic crisis,'' he told an audience in Monterrey late last month. His figures project an increase in net income of 38 percent over 1982, for an estimated $850 million surplus.
The change, as many in Mexico these days, has come extraordinarily swiftly. In the past 12 months, the value of the peso nose-dived from about 4 cents US to about 0.66 cents. And while a rampage of inflation has pushed prices up by about 100 percent in the same period, the overall effect has been to bring Mexico (in the tourist's eye) from slightly too expensive to dirt cheap.
So since late 1982, when the outside world began to catch on to the values here, resort areas (though not Mexico City itself) and airline flights have been heavily booked.
The week preceding Easter, a holiday that virtually shuts down business here as Mexican families flee to beaches and mountains, was especially heavy. Coinciding with US school vacations, it drew so many tourists that the US Embassy here issued a travel advisory warning visitors to the popular state of Sinaloa on the Gulf of California to be sure they actually had the rooms that had been reserved for them.
The advisory, which drew the wrath of Sinaloa officials, was intended to alert travelers to some reported problems of overbooking, problems that officials here are beginning to recognize. Mr. Goicoechea warned against what he called the ''petrolization'' of tourism, an analogy to what he sees as the Mexican oil industry's efforts to squeeze the greatest benefits in the shortest time rather than build for the future.
And a report by the American Chamber of Commerce of Mexico notes several trends: a weekly readjustment of prices (making it difficult for travel agents to guarantee the cost of package tours), and ''a system of two hotel rates - one for foreign tourists, and one for Mexicans.''
The report also points to ''real or imagined fears'' among potential visitors that ''Mexico may be on the brink of social upheaval.''
So far, however, tourism is showing steady improvement, registering a 15 percent increase nationwide in numbers of tourists during January and February. Also increasing are charter flights, following a period that saw international travel on two of the nation's leading airlines decline from 3.1 million passengers in 1981 to about 2 million in 1982.
The flip side of the travel coin, however, shows a virtual drying up of trips abroad by Mexicans. Accustomed to extensive travel during the oil-boom years, they have seen the cost of foreign vacations shoot up by 500 percent in the past year.