In today's militaristic Managua normally no one would think twice about the uniformed men sometimes seen around the bland, tidy little house in the fashionable Las Colinas neighborhood.

But the house is the embassy of the Palestine Liberation Organization and the men are believed by neighbors to be Palestinian soldiers.

According to informed Western officials there may be 20 to 25 Palestiniantechnicians and pilots here working with the Nicaraguan armed forces.

Their exact duties remain unclear, but they are thought to play an important role in maintenance and radar duties in Nicaragua's Air Force. Conversations with Palestinian and other diplomats suggest that these soldiers are also here to open up another front in the PLO's worldwide struggle against Israel, with the Palestinians backing the region's revolutionaries and the Israelis most often helping out Central America's more conservative established governments.

Representatives of both sides acknowledge that the most attractive charm they have to offer prospective allies is military expertise and arms.

The Somoza dictatorship's National Guardsmen, defeated here in the 1979 insurrection, looked like peasant copies of Israeli paratroopers. Guatemalan troops still do, carrying Galil assault rifles, wearing distinctive Israeli belts and helmets, and traveling in slightly pregnant-looking Israeli Arava light transport planes.

A brand new Israeli communications school to be used primarily for military purposes was inaugurated in Guatemala City last year and Israel has been considered by members of the new Costa Rican government as a possible source for equipment and training in the reorganization of that country's security forces.

The defeat of Somoza opened the way for the PLO to gain a major foothold in the region. Palestinians had helped to train Sandinista commanders before 1979.

In July 1979 a PLO-chartered aircraft ostensibly carrying relief and medical supplies between Beirut and Costa Rica for Nicaraguan war refugees was found during a stopover in Tunis to have 50 tons of arms, including an antiaircraft gun, on board. The Tunisian government ordered the cargo unloaded.

The PLO has since helped train and arm other Latin American guerrilla groups, including El Salvador's insurgents, but the extent of this activity remains murky.

In January, PLO chairman Yasser Arafat was quoted in Beirut's As Safir newspaper as saying his group had sent pilots to Nicaragua and guerrilla fighters to El Salvador.

The remark was not published in the PLO's own WAFA news bulletins, but a PLO spokesman in Beirut made an official statement afterward that "we will not hesitate to send arms and people" to guerrillas in El Salvador since "our policy is to help revolutionary movements everywhere to the extent possible."

The Palestinian charge d'affaires here, George Salameh, recently expanded on this idea.

Referring to Arafat's January statement, Salameh said, "What Commander Arafat means is that we do indeed aid our friends in this aspect . . . If Commander Arafat said that we have pilots and even combatants that means it's true."

Asked for specifics, Salameh said, "there is not the slightest possibility of mentioning figures," but suggested they are not high.

"The number doesn't count. It's the fact in itself," said Salameh. "A small thing is sometimes more significant."

Independent sources who have looked closely at the PLO's activities in the region believe that the Palestinians are probably acting more in an advisory than a combat capacity, especially with regard to the Salvadoran guerrillas.

Arafat visited Managua in July 1980 at a time when Cuba's Fidel Castro and other leftist revolutionaries were gathered here to mark the first anniversary of the Sandinista triumph and reportedly to plan major arms shipments to the Salvadoran insurgents.

But mainline leaders in the PLO's coalition of eight guerrilla groups appear to have a limited interest in Latin America, and initial links to this region, at least, were promoted by partisans of the more radical Naif Hawatmeh and George Habash.

As was the case in Nicaragua, PLO ties to the Salvadoran rebels were enhanced by the Palestinian origins of some Salvadoran insurgent leaders.

Shafik Handal, the head of the Salvadoran Communist Party, is the son of a Palestinian who emigrated to El Salvador from Bethlehem in 1921, although Handal himself is not reported to speak any Arabic.

Handal was hosted by Hawatmeh and hisfollowers in Beirut in March 1981, a period when the Salvadoran guerrillas were regrouping and rebuilding supplies after a failed "final offensive" three months before. Hawatmeh introduced him to Arafat's Fatah and to leaders of Habash's Popular Front for the Liberation of Palestine.

Handal's traditional Soviet-line party was the last of the five factions in El Salvador's current guerrilla front to adopt a strategy of "armed struggle" in 1980 and as a result had to rush to equip its relatively small forces.

As Safir's coverage of Handal in Beirut suggested without explicitly stating it that Salvadoran guerrillas would be trained by the PLO as some Sandinistas had been.

Handal was quoted as saying, "We and the Palestinian revolution are in complete understanding" and concluding, "We intend to strengthen our solidarity with the rest of the Arab liberation movements. This is because we all struggle against one enemy, Israel. Alexander Haig is right in expressing anxiety over this alliance."

As Salameh commented here, "It is not incumbent on us to fight directly the presence of our enemy in the exterior. But we do have a role to play, which is to gain friends. In that we indirectly strike a blow at the presence of Israeli Zionism in Latin America generally and in Central America in particular and we reduce the camp of the enemy."

"We are not living in the 1920s when a revolution could begin, stay in its own boundaries and be fought with no one paying attention," said Salameh. "With an isolated revolutionary movement it's very difficult to survive."

Training Latin American guerrillas, Salameh said, "was something logical. One expects a revolutionary to offer this type of aid as part of his solidarity."

"Within our possibilities we give what we can to our friends," Salameh continued. "Our aid is not limited, shall we say, to the economic."

The Palestinians have supplied various types of economic help as well as military advice and contacts to the Sandinistas.

Since the Sandinista triumph the Palestinians have been instrumental in forging links between Managua and the Arab world and opening it up as a source of aid.

"We have played a pretty important role," said Salameh. "We were helpful with the loan from Libya" that helped bolster Nicaragua's crippled economy a year ago with $100 million.

The Algerians, meanwhile, supplied arms, including Soviet-made tanks, to the rapidly growing Sandinista Army.

The Palestinians themselves reportedly contributed between $10 million and $12 million to the Sandinistas just after the insurrection.

Strapped for funds again this year, the Sandinistas are now looking not only to ties with the radical Arab states, but with more conservative Middle Eastern governments.

"We are trying to tighten relation with the Saudis, Kuwait, the United Arab Emirates through the good offices of the PLO," said one senior Sandinista diplomat.

Salameh emphasized Palestinian work "to open an Arab market for Nicaraguan production, which is much more important than just loans."