More than 1,000 Argentines gathered at dockside today in a raucous welcome to the first boatload of war prisoners to return here, a group of 188 soldiers, sailors and civilian workers, captured on the South Georgia Islands April 25.

Ticker tape fluttered from the tops of skyscrapers overlooking the sunlit bay, as the lumbering gray ferry Piloto Alsina sailed in from Montevideo, Uruguay. The prisoners and relatives cried, laughed, waved Argentine flags, shouted, "Viva la patria" (Long live the fatherland) and sang the melodious verses of the national anthem.

Despite the jubilant celebration on the docks and an apparent pause in the fighting, however the atmosphere in official circles here seemed closer to a death watch as speculation and rumor continued to spread through the capital over when or whether the British would invade the Falklands, known here as the Malvinas Islands.

Foreign Minister Nicanor Costa Mendez continued to insist he was "optimistic" about the outcome of talks at the United Nations, but he said he had no immediate plans to travel to New York, a sign that negotiations had not progressed very far.

In an interview with Peruvian television today, President Leopoldo Galtieri said, "Argentina is prepared to counter British forces with its air power and give battle." On the U.N. talks, he said, "All negotiations are delicate, difficult," and added, "There is a slow advance, but one does not yet see the final form of the issues we are dealing with."

If necessary, Galtieri said he would request aid from other Latin American countries. "The Malvinas Islands have become not only Argentine, but also Latin American," he said.

The job of the U.N. secretary general, Galtieri noted, is "arduous, intense, speaking to both parties and listening to points of view. I think that while there is still possibility of a dialogue at the level and with the prestige of Secretary General Javier Perez de Cuellar, there are chances of arriving at a solution. The problem will come if the intervention of the U.N. secretary becomes frustrated or cut off."

The prisoners, who were flown yesterday from Ascension Island to Montevideo in a Dutch DC10 airliner, included 80 crew members of the Santa Fe submarine, 39 civilian workers who had been dismantling a whaling station and other military personnel who had assisted in Argentina's capture of the island April 3, a day after the Falklands invasion.

Missing, however, was garrison commander Alfredo Astiz, whom the British were reportedly holding at Ascension Island. The Swedish and French governments want to speak with Astiz in connection with the disappearance of two French nuns and a Swedish citizen in 1977, in the midst of the Argentine military's violent campaign against leftists and guerrillas.

The government took a low profile in today's arrival of the prisoners. No military bands greeted them and no official ceremony was held, at least in public. Most of the soldiers were loaded onto buses to return to military bases in the south.