Wearing Ray-Ban aviator sunglasses and flight suits, the two U.S. military advisers warily approached more than 50 reporters assembled to meet them today.

Sent to El Salvador a month ago to train pilots and mechanics for the new fleet of six UH1H (Huey) helicopters shipped here to flight leftist guerrillas, their jobs are similar to those of U.S. military instructors scattered in more than a score of countries around the globe. The only difference -- as one of them points out -- is that "Salvador in the situation that it is."

Because world attention has been focused here by the White House, because their presence echoes in the minds of many Americans as the first step into the lightless tunnel of another Vietnam, because they know they are walking targets for extremists who may try to provoke an even larger conflict, they know that they and about 30 other U.S. advisers currently here are indeed different.

They speak fluent Spanish. They refused to give names or ranks or serial numbers to the press clustered at the entrance to the military air base at the former international airport seven miles east of here, and when they spoke to reporters they spoke in military jargon.

"Negative," said the flight instructor when asked if the new helicopters have an offensive capability with their new machine guns mounted in the doors.

"Negative," he answered when asked if he has flown or will fly into combat here.

So far the biggest worry for these advisers has not been facing the guerrillas but facing the 50 foreign cammeramen and reporters who have descended on this war-weary, big-story little country.

"What makes you nervous," said the mechanic-instructor, "and I'll be honest with you guys, is the press. We have more problems with the press than these people. We're supposed to be aware of . . . when someone sticks a camera in your face it makes you something special that you're not, really. It makes you something . . . to people who might want to use that."

Exactly what it makes them, they believe is clay pigeons for any of countless terrorists at large in El Salvador. As another adviser who briefly met a reporter by chance put it, "We don't want to die here."

That fear appears to be justified.

The advisers stressed that they do not fly into combat. They stay close to the Ilopango military airport or the new international airport, an hour's drive from here, when teaching and do not fly beyond the traffic pattern.

But, although they do not look for it, combat could easily find them as they serve out their six-month tours. Little battles break out like the plague almost anywhere at almost any time in this bitterly divided nation.

"We're not to get involved in any fighting activity unless it is self-defense," said the flight instructor. "But if I see one of my members [of the U.S. training team] is about to get killed or something I'm going to take some action."

At this stage of the war these U.S. soldiers in El Salvador seem impressed with the quality of the men they are training.

Said the mechanic, who served in Vietnam, the Salvadorans "are very capable. Their ingenuity is amazing."

The mechanic said that there was no comparison between El Salvador and Vietnam, but then he said that the Salvadoran soldiers are "superior in their organization, their discipline and their motivation level."

That is one of the reasons, said this young officer, that he firmly believes the Salvadoran Army can win its fight against the gurerrillas. He did not speculate as to how many others like him would have to help in the process.

These two advisers were insistent in their belief that there would be no big escalation here. Those who feared such things, said the mechanic, are "idealists."

"They have no idea," he added. "People who are saying we should not be involved here when so many other countries are involved, they're not aware."