MEXICO CITY, OCT. 13 -- Two months after the signing of an agreement for which Costa Rican President Oscar Arias today won the Nobel Peace Prize, the Central American governments and insurgencies involved have made greater progress than expected toward complying with the accord.

But not quite a month before the regional cease-fire is to take effect, it is still not clear whether the compliance will amount to more than collectively going through the motions of peacemaking and actually end the rebellions, repression and economic destruction that have devastated Central America.

And, in one of numerous details that the plan seems to have glossed over, no provisions have yet been made to finance such endeavors as an international verification commission and a Central American parliament.

The main cause for hope is that the peace plan, largely authored by Arias, has generated momentum since it was unexpectedly signed in Guatemala Aug. 7 by the presidents of Nicaragua, El Salvador, Honduras, Guatemala and Costa Rica.

In reaching such an important agreement by themselves, the signatories assumed a vital stake in the accord's success -- or at least in the appearance of complying with it -- and demonstrated a growing sense of regional independence from the United States.

"The United States must come to terms with the fact that a motley collection of Central American countries is finally coming of age," a European ambassador in the region said recently. "It is an agonizing process."

On the other hand, a major cause for pessimism is that, as a diplomat in Honduras put it, "this agreement is not underwritten by enough good faith or compulsion to make people comply." Instead, he said, "success is based on all the countries doing a fairly complicated ballet, and gradually little bits and pieces will get out of kilter."

So far, the main accomplishments under the peace plan have been the creation of national reconciliation commissions in all of the countries except Honduras, the initiation of formal peace talks between government and rebel representatives from El Salvador and Guatemala, and a political opening in Nicaragua.

The Sandinistas have restored some freedom of the press, allowed exiled church leaders to return, released imprisoned foreigners accused of counterrevolutionary activities and opened greater space for opposition political parties. They have done nothing so far to diminish the control of the ruling Sandinista National Liberation Front over the armed forces and state security apparatus. Nor have they taken any action suggesting a change in their view that the front ranks as the country's revolutionary "vanguard" and occupies a place in society on a par with the state.

To further demonstrate compliance with the peace plan, the Sandinistas have called limited unilateral cease-fires in three specific areas of the country and have been seeking contacts with contra field commanders regarding an amnesty. But they have refused to talk to the contra leadership about a negotiated cease-fire or other peace provisions on grounds that these leaders are puppets of the Reagan administration. The pact does not require governments to meet with armed opposition groups.

In El Salvador, President Jose Napoleon Duarte last week held talks in the capital with leaders of a rebel alliance made up of the Farabundo Marti National Liberation Front and the Democratic Revolutionary Front. They agreed to set up two joint commissions to seek a negotiated cease-fire and agreements on other provisions of the Arias peace plan. But the Oct. 4-5 meeting produced no softening of the rebels' fundamental demand for participation in a "transition" coalition government or of Duarte's insistence that the rebels abandon violence and join the political process.

Duarte said that if the cease-fire commission was unable to reach an agreement by Nov. 5, he would declare a unilateral cease-fire to comply with the peace plan's provision for Central American truces within 90 days of signing.

In Madrid, representatives of the Guatemalan government and a rebel coalition called the Guatemalan National Revolutionary Union last week held the first formal peace talks in that country's 26-year-old guerrilla war, but reached no agreement beyond pledges to study each other's proposals.

Both sides called the Oct. 7-9 talks a first step toward peace but declined to say if they would meet again. The talks appeared to founder on the government's demand that the estimated 2,000 rebels lay down their arms and the guerrillas' refusal to do so without a broad political agreement.

In Honduras, there has been no sign yet of moves to comply with the peace plan's prohibition on rebels' use of one state's territory "to destabilize" another -- a provision that Nicaragua says requires the removal of contra bases and other facilities from Honduran soil.

El Salvador, meanwhile, has formally demanded the dismantling of Salvadoran rebels' installations and support activities in Managua and an end to aid that the Salvadoran government says is flowing to the rebels from the Sandinistas.

Ascertaining compliance with the peace plan's provisions is the province of an International Commission for Verification and Follow-up, composed of 13 Latin American foreign ministers and the secretaries general or representatives of the United Nations and Organization of American states.

The foreign ministers represent the five Central American signatories, the members of the Contadora Group -- Mexico, Panama, Venezuela and Colombia -- and a "support group" consisting of Peru, Uruguay, Argentina and Brazil.

No provisions have been made to fund this commission, which presumably must travel extensively and marshal considerable resources to discharge its duties.

Nor has there been any commitment to financing the establishment of a Central American parliament, which is to be set up next year in Guatemala with 20 elected representatives from each of the five signatories of the plan.

Costa Rican Vice President Jorge Manuel Dengo acknowledged recently that the Central American states "will have to make a big economic sacrifice" to implement the peace plan. He said he hoped that contributions would come from the European Parliament, the model for the new Central American body, and "maybe from U.S. civic groups."

The awarding of the Nobel Peace Prize to Arias could make that quest for funds somewhat easier.