Though the Cubans haven't had an awful lot to celebrate lately, yesterday they put on their best nonaligned faces, served up French champagne and managed to get through Cuba's National Day, anyway.

A lot of the Third World diplomatic crowd was there, which was no surprise, but so were some people you might not have expected to see. The Chinese, for instance.

Ramon Sanchez-Parodi, head of Cuba's Cuban Interests Section housed in the elgant old 16th Street NW mansion where the party was held, said the presence of Ambassador Chai Zemin didn't surprise him in the least. s

"We have normal diplomatic relations," said Parodi, adding that "the fact they are here is part of the usual diplomatic practice.

Chai more or less supported that but with the qualification that "we want to develop our relations with Cuba but it's a question not to be decided by us only but by the Cubans also."

At least one guest made no effort to mask his surprise.

"It's really bizarre," said Myles Frechette, director of the Cuba desk at the State Department and thus a close follower of Cuba's international relations.

There were some Russians at the party, along with some of their Commumist bloc cronies like the Poles, Romanians and Czechoslovakians. There were representatives of Cuba's Caribbean neighbors, Barbados and Jamaica, and Latin American countries like Costa Rica and Nicaragua and about 250 other visitors, many from U.S. officialdom and U.S. business.

So the talk had a way of getting around to Afghanstan and Iran -- diplomatically, mind you. The failure of Cuba to win a seat on the United Nations Security Council caused one Third World diplomat to heave a sigh of relief.

"The presence of Cuba would have strengthened the Soviet's position, and there were a lot of us clearly not in favor of what the Soviets are doing in Afghanistan," said the diplomat, asking not to be identified -- "for obvious reasons."

The U.N. vote "deploring" Soviet intervention and calling for a complete withdrawal of foreign troops only pointed up "the kind of change taking place" among nonaligned countries, said Ambassador Chai, speaking through an interpreter.

Cuba's support of its Soviet allies, Chai continued, "tells us which way Cuba will go -- people will have to judge by their actions and deeds."

Nicaragua's Ambassador Rafael Solis, minus his Sandanista beard and fatigues -- and clearly uncomfortable in his pinstripe suit, took the neutral position to "maintain balance."

The diplomats didn't hold a monopoly on global discussions. Florida citrus grower W. R. Hancock Jr. talked about the Cubans in the world market place; Ed Theobald of New Hampshire talked about the business (his, actually) of exporting utility poles, and Tedd Miller of the National Conference of Black Lawyers came down on the side of the Soviets in Afghanistan.

"The assassination [of Afghanistan's president] was part of the coup, not by the Soviet Union, but an internal matter," said Miller.

Yet if one recent event had an effect on the Cubans' birthday party yesterday, Sanchez-Parodi said it was "inflation."

They made a gesture toward fighting it by calling the party a "coupe de champagne" and serving a midday spread of tea, sandwiches and petit fours. There wasn't a Havana cigar in sight.