If there is one less on this small Central American nation has learned from President Carter's human rights policy, it is importance of having friends in Washington.

While grudgingly admitting to certain deficiences in its governmental respect for the rights of peasants political opponents and activist priests, El Salvador attributes much of its increasingly bad image in the United States to bad public relations.

Many here share the increasingly widespread conviction in many Latin American countries that human rights criticism, as dished out by the United States, is reserved for countries that are innocent is the ways of Washington.

Charges of fraudulent election, the killing of protectors and explusion of several priests here brought two congressional hearings, critisim by Secretary of State Cyrus Vance and American church leaders, and threats of U.S. economic and military sanctions.

El Salvador, whose rural economy has long been controlled by a closed coalition of the military and the wealthy oligarchy, is fisding taht the righteous wrath of the United States can be very costly.

Since the administration began to look at this country's human rights record, there has been a decline in the tourist and convention trade, a slowing of outside and domestic investment and, at least temporarily, the U.S. speaking of a $90 million international loan request for a new hydroelectric project.

If the United States decides to follow through with loan vetoes in miltilateral lending banks, it could cost much more. Some informed observers say it could bring El Salvador's entire development program, and perhaps its whole economy, crashing to the ground.

El Salvador has no industry to speak of no strategic importance, and his traditionally existed by the sweat of the brow of its peasants, the careful borrowing of enough money to grew at a small's pace, and the benevolent smile of the United States.

For the reasons, El Salvador may be one of the few countries in the world to respond positively to Carter's human right's policy. Already, small but important changes have begun.

Following a personal expression of concern by Secretary of State Cyrus Vance over threats against Catholic priests by rightist terrorists here, allegedly linked to government security forces, President Romero this week began regular meetings with local church leaders.

For nearly a month after the terrorists gave Jesuit priests 30 days to leave the country or face systematic execution, Romero made m no comment on the threat. Monday, three days before the deadline, and the three days before the start of congressional hearings in Washington on the problem, he publicly denounced terrorism and said he would fight it, whether it came from the right or the left. So far no priests have left the country and none of the threatened Jesuits have been killed.

"We don't have the kind of image builders in Washington that some other countries have," said Lt. Col. Rafael Flores Lina, information minister for President Carlos Humberto Romeno.

As evidence of what good public relations can do for a country. Flores Lima and other Salvadorean officials point to lobbying efforts by South Korea and even closer to home, by neighboring Nicaragua. While Nicaragua has also been accused of human rights violations its lobbyists have managed to prevent serious sanctions.

Nicaragua has a large information or lobbying office in Washington El Salvador a poor country that is the smallest and most densely populated nation in the continental Americans, has only an embassy, and small one of that. With an annual budget of around $100,000, it is headed by an ambassador who doesn't speak English.

While El Salvador was being criticized last months Nicaragua's information office, with the high-powered help of a former congressman and former Navy secretary, worked to defeat an effort by congressional liberals to elminate all U.S. military assistance so that country.

The Nicaragua sanction was subsequently removed from the Foreign Assistance Bill during a House floor debate, a loss that its backers attribute to Nicaragua lobbying pressure.

Nicaraguan President "Anastasio Somoza" is a smooth, intelligent guy, one source close to the Salvadorean, government said with admiration. He pointed out that Somoza attended West Point, making good contacts with future political and military leaders.

"We are seriously considering sending somebody from here to West Point, just as a long-term investment," he said.

There are plans afoot in El Salvador to beef up its Washington embassy - with more U.S. - attuned diplomats.

"If our embassy could be more aggressive in trying to communicate, in a positive sense" to Congress and the administration, Flores Lima said, perhaps the United States would be more understanding.