President Reagan today celebrated Easter in the Caribbean and then returned to Washington to face crucial economic and foreign policy decisions.

Aides said that Reagan had not yet accepted a proposed budget compromise that would keep the fiscal 1983 deficit under $100 billion but would also undercut the administration's tax reduction program by adding a 4 percent income surtax that might be applied only to upper-income taxpayers.

Other options being studied for the budget proposal include a $5 per barrel fee on imported oil and an excise tax on energy products other than home heating oil.

The administration officials, while declining to discuss any details of the budget options, emphasized that neither the president nor House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) had approved the proposal. One unresolved question is how much Reagan would be willing to trim the defense budget. "There's still a lot of work to be done," said one aide.

As the president completed a five-day Caribbean trip that White House officials have called a "working holiday," the issue that seemed to be uppermost was the continuing dispute over the Falkland Islands.

Secretary of State Alexander M. Haig Jr., who has been attempting to mediate the Falkland islands dispute between Britain and Argentina, returned to London today. The president talked with Haig twice on Saturday, but declined to discuss the conversations with reporters.

"I can't comment," Reagan said, shaking his head as he and Nancy Reagan entered St. James Parish Church in Holetown on Barbados' north coast for the Easter service.

Security was tight and admission was by ticket only at the 108-year-old Anglican church, which is built of Barbadian coral. The Reagans, neither of whom is an Episcopalian, took communion at the altar, kneeling as they celebrated the Eucharist.

St. James' rector, George H. Dickenson, delivered a sermon on sin. The congregation prayed for the poor and the sick and "especially for a peaceful settlement between Great Britain and Argentina over the Falkland Islands."

About 400 people, who were screened for weapons before entering the church, attended the service. Secret Service agents sat behind the Reagans and another agent stood facing the congregation.

After church, Reagan said that his vacation here was "just fine," but some White House advisers were touchy about the flood of television and newspaper accounts showing Reagan vacationing at a critical period in his administration.

However, the president seemed less concerned. He swam boldly in a strong surf Saturday and waved to television photographers who were aiming their cameras from a hotel just beyond the limits of the secluded beach where he has relaxed the last three days.