Mexico City — The tables in the Sheraton Hotel's finest restaurant are still laid with silver plates on thick white linen. But the grand piano near the dance floor is desperately out of tune.
Mexico itself, these days, is a land of discordant promise, a nation of former elegance unsure how to take itself into the future. To ask where the country is headed is to encounter a surprising degree of uncertainty - together wtih a clear recognition of its potential.
''I am optimistic, and I am convinced that this country has great resources in every respect,'' says a Mexican business executive.
But a political economist, who wanted his name withheld for fear of government reprisals, said that the de facto one-party system could not last the next six years in its present form. ''What we're afraid of,'' he added, ''is that the oligarchy does not recognize that it has to step down or reform.''
But many would agree with the head of a group of American businessmen who says that ''there are more prospects than problems.'' He and others list the nation's strengths as:
* Superb geopolitical location, close to major markets in the United States and of such strategic importance to Washington that it cannot be allowed to collapse.
* Rich natural resources, including not only oil but also silver, copper, tin , coffee, cotton - even honey, of which Mexico exports more than any other country.
* A solid infrastructure of highways and communications, one of the most advanced among developing nations.
* A tradition of controlled democracy generally seen as second only to Costa Rica's among Latin American nations. Although a Mexican scholar notes that ballot boxes out in the provinces are routinely stuffed - that, in his words, ''Chicago-style tactics are practiced in this country'' - it remains true that governments change here (as happened last December) without military intervention or the assassination or exile of former leaders.
But the uncertainty is also evident. As austerity replaces opulence, ''Everybody is suffering,'' says Angel Gurria, Mexico's director-general of public credit.
A recent report by DIEMEX-Wharton Econometric Forecasting Associates describes the next three years as an ''extremely precarious period'' requiring ''a most severe recovery treatment.''
The director of a privately funded think tank here agrees: ''For the middle class, the next two (years) are awful, and the following two are bad.''
Economic forecasters in and out of government, in fact, seem almost to be competing for the direst predictions - prompting a provincial newspaper to come up with a recent headline reading, ''Enough of realism, let's go back to promises.''
One of the promises repeated vigorously during President Miguel de la Madrid Hurtado's election campaign last year concerned the need to reduce widespread corruption among government employees. Mexicans and Americans interviewed here agree that the success of the new administration will be measured in part by its ability to deal with this issue.
Already, says a high official in the newly established Controller General's Office (akin to the US General Accounting Office, but with the firm backing of the President), the government has rounded up some 15 senior officials on corruption charges, and has compelled the head of one state-owned corporation to return three automobiles he had purchased at federal expense. By midsummer, says this official, his office will be ready to take more serious steps.
But the one step many Mexicans wish most to see - the prosecution of former President Jose Lopez Portillo and some of his close associates on charges that they enriched themselves at the nation's expense - seems unlikely to occur. President de la Madrid is known to feel that, as Mr. Lopez Portillo's handpicked successor, such a prosecution could cast his own past into doubt.
The corruption issue is as much symbolic as economic, however. Students of Mexico's fiscal situation say that weeding out corruption might not, in the end, make a very large dent in the budget deficit.
''Corruption is a form of tax,'' notes a Western diplomat, who points out that low wages for such public-sector workers as policemen would have to rise if their ability to earn extra money through payoffs were severely curtailed.
Will the need for austerity push Mexico, accustomed to exceptional wealth during the recent oil-boom years, toward social turmoil?
With the combination of unemployment and ''underemployment'' estimated to be in the range of 40 percent, government officials are clearly concerned. Speaking of ''social unrest,'' Mr. Gurria says that ''to the extent that we cannot have the levels of employment that we've had in the past, clearly you will have pressures.''
The pressure, ironically, comes because so much progress was made during the oil-boom years, raising the expectations of the average Mexican. Since the mid- 1970s, the nation has poured tremendous resources into dams, roads, electrification, communication networks, and schools.
Six years ago, recalls a newspaper editor, Mexico City had electrical ''brownouts'' almost daily. Now, she adds, ''I think that most people are living 50 percent better than they were six years ago.'' Many working Mexicans share that perception.
Now, however, Mexicans are still waiting to see where the new administration will take them. ''There are lots more good questions than there are answers,'' says an American business executive residing here.