To some Filipinos they are "foreign meddlers." To others, generally opponents of Philippine President Ferdinand Marcos, they could play a key role in assuring a fair presidential election Friday.

Close to 100 foreign observers who will be on hand for the voting, but they will cover well under 1 percent of the country's 90,000 polling places and will have no authority to stop any cheating that they see.

By law, they will be barred from polling stations when voting is taking place. Much of their schedules will be known in advance by Filipino officials, and almost none of them will be competent in Tagalog, the national language.

Despite these limitations, much of the outside world will look to them for an independent evaluation of the fairness of the election, which is to be conducted in a country notorious for fraud at the ballot box.

In particular, whatever conclusion they announce could have a deep effect on relations with the United States. President Reagan has said that he will seek increased aid for the Philippines if the election is conducted fairly and if the winner carries out a program of reforms.

Three separate groups will be present:

A 20-member official U.S. delegation named by President Reagan and led by Sen. Richard Lugar (R-Ind.) and Rep. John P. Murtha (D-Pa.). It arrived tonight.

An international group organized by the U.S. Republican and Democratic parties. Its 44 members include a former president of Colombia and a member of the British Parliament from Northern Ireland.

Seventeen teams made up of officials from the U.S. Embassy and other diplomatic missions in Manila . The U.S. Embassy in recent days has brought in from abroad Americans with experience in the Philippines for temporary duty on election day.

The observers were invited formally by Marcos, but some members of his ruling New Society Movement party seem less than enthusiastic about their presence.

The U.S. Embassy here is viewed by them as favoring Marcos' opponent, Corazon Aquino. U.S. press reports that Washington is preparing to distance itself from Marcos has added to the mistrust.

"We are neither awed nor fazed anymore by anything America does in the pursuit of its interventionist policy in the Philippines," the progovernment Philippines Daily Express said in an editorial last week entitled "Observers or Meddlers?"

In a press conference, J.V. Cruz, a spokesman for Marcos' ruling party, welcomed the observers but said they must not interfere. He said it was hard to see how such a small number of people could get a total picture of what goes on in the voting and questioned whether they were familiar with Philippine electoral practices.

"People guiding friends and relatives to the polling booths, offering food -- I think practices frowned upon by the election code but hallowed by tradition," he said.

Criticism also has been heard in Washington and Manila that sending a U.S. team would in itself put a stamp of approval on the vote, in view of Marcos' tight control over the political process here.

In Aquino's camp, however, it is hard to find those who would rather the observers stayed home. Opposition members generally say Marcos' party intends to commit fraud and will find it hard to do so if foreigners are present.

"Maybe that will serve as a deterrent for cheating," Aquino told reporters last weekend.

The observers' presence also is applauded by Namfrel, a citizens' group that is theoretically a neutral monitor of the voting but is widely perceived as being in the Aquino camp.

Its chairman, Jose Concepcion, says that election workers have been pleading with him to send foreign observers to their areas. He holds it out as an example of how low the political process has sunk that Filipinos must look abroad for such protection.

The teams are being briefed by Namfrel, by the government's commission on elections and various other officials. Their stations will be selected from about 150 places that have been identified by Namfrel and others as trouble spots, Concepcion said.

The election law requires that outsiders stay more than 50 yards away from polling places. But members of the delegations maintain that any widespread fraud will be apparent.

"I know exactly what I'm looking for," said John Hume, a British member of Parliament from Northern Ireland. He cited his experience in Northern Ireland as having helped prepare him.

Brian Atwood, a staff member of Hume's delegation, said today that Philippine officials had told them a watermark machine used in printing ballots and vote counting sheets was missing for eight days after Marcos proposed the election in November. That raised the possibility that it had been used to print fake ballots.