Two weeks ago, as Congress was debating covert aid to Central America, Rep. Robert Garcia (D-N.Y.) expressed the fear of some Hispanic-Americans that the United States could be edging toward war.

Garcia said he wanted his congressional colleagues to know "that it's not going to affect the young people in many of your districts . . . . I will tell you who is going to fight a war. It is going to be a lot of young Hispanics and blacks from the Southwest and from the Northeast who will go in there."

Other Hispanic leaders say there is growing fear among Latin Americans who have begun to build a better life in the United States that their young will be sent back to the countries they came from, to fight their relatives.

"The biggest dilemma we will face will be to fight for America as Hispanics against other Hispanics," said Arnoldo S. Torres, executive director of the League of United Latin American Citizens (LULAC), the nation's oldest and largest Hispanic organization. "If there is a war, Hispanics will go to war for America, but for us it will be to kill our own.

"There may be a backlash against the Hispanic people in this country if we go to war in Latin America," Torres added. "We have problems now with immigration officials who mistake us for undocumented aliens. To look like the enemy and talk the enemy in a war, you can understand, we may fear that we will be viewed as communist sympathizers . . . . There will be spillover effects on Hispanics in this country."

Yet among the most vocal supporters of President Reagan's policies in Central America, at the urging of the White House, are Republican Hispanics who dismiss any concerns about Hispanics here fighting other Latin Americans.

"The Cuban people who left Cuba because of Castro want to go back and fight, don't they?" asked Dr. Tirso Del Junco, former chairman of the California Republican Party, co-chairman of the Republican National Hispanic Assembly and a long-time Reaganite. "We will fight as Americans against communism for the good of America.

"Why should we be any less concerned than the Anglos about El Salvador and Nicaragua falling to the communists?" he asked. "If Salvador goes communist it will increase the illegal aliens coming in and jeopardize the jobs of Hispanic-Americans. The only ones saying anything different are the liberal Democrats in the Hispanic community, not the people."

Reagan is scheduled to speak to several Hispanic groups during a three-week vacation away from Washington beginning Friday, and the central theme of his speeches to the Hispanics is expected to be that they need to communicate to other Americans their firsthand knowledge of the impact of communism on Nicaragua and Cuba.

"You, as leaders in the Hispanic community," Reagan told a group of 85 politically active Hispanics from the Southwest at a White House luncheon last Friday, "can serve as a bridge to our understanding our neighbors to the south. I hope to work closely with you on this and on other challenges that we face.

"You, as Americans of Hispanic descent, know well that our country ignored Central and South America for too long," he said. "If we're to prevent the people of this important area from falling under the heel of Marxist dictators, spreading instability to our own borders, its going to take a determined commitment. It will require economic and military aid and national resolve . . . , and so we're standing by our friends."

However, in a speech Monday to the National Hispanic Voter Registration Conference in San Antonio, Democratic Gov. Toney Anaya of New Mexico stressed that while Hispanic-Americans may be familiar with the problems of communism in Latin America they cannot be counted on to oppose communism at any cost. "Our agenda is as universal as the issues are grave," said Anaya. "We care about a defense budget that runs amok while our children go uneducated, unfed, unclothed and with no health care. We care about a sensible U.S. policy or lack thereof in Central America."

Interrupted with the loudest and longest ovation of any speaker at the conference, Anaya added: "If this and previous administrations would utilize Hispanics in key policy-making positions . . . our relations with our brothers and sisters in Latin America would be much different--we would be exchanging trade instead of trading exchanges . . . be encouraging the growth of democracies instead of giving meaning to the nightmare of gunboat diplomacy that can only result in giving us years of open war or decades of guerrilla warfare."

Reagan's political advisers have him talking to Hispanics not only because of the need to bolster support for the administration's Latin American policies but because Hispanics, despite registering Democratic at about an 85 percent rate, are seen as a potentially strong voting block for Reagan if he seeks reelection.

Before Reagan spoke to Hispanic group at the White House last Friday, Vice President Bush, Reagan's chief political adviser, Edward J. Rollins, and Reagan's chief of staff, James A. Baker III, addressed them in the Old Executive Office Building and told them how important they are to a 1984 Reagan-Bush ticket.

"They said the administration and Hispanics have shared values like school prayer, stopping abortion as well as fighting communism," said Helen Knaggs, of Austin, who attended the lunch as well as Reagan's speech and a question-and-answer period.

"Hispanics in this country are Americans first," said Manuel D. Leal, a Houston lawyer who also went to the lunch. "The president talked not only about Nicaragua but about the economy . . . , people coming from south of the border to escape communism will be taking our jobs. That is a real concern for Hispanics here, and the president knows that. We will be loyal to our country and to our president."

Hispanics often cite Mexican-Americans as having won the most Medals of Honor of any ethnic group. "Hispanic Americans will fight when and where they are told to for America," said Emily McKay, executive vice president of the National Council of La Raza.

"We are a community-based organization and we hear the fears," she added, however. "There is no question that the community is very aware of what is happening in Latin America and aware that it could make for xenophobia here against all Latins, even if their home is in the United States."