The three heaviest hitters in the Reagan Cabinet were sent to bat before restless conservatives yesterday.

No one hit a home run or struck out. Mostly, they scored with ground ball singles.

The hottest pitches at the annual Conservative Political Action Conference were thrown at Treasury Secretary Donald T. Regan.

One student asked, "If President Reagan can't balance the budget, who can? " Another well-dressed conservative suggested the government should simply shut down for a while rather than continue to run up deficits.

And a 69-year-old conservative from Buffalo, N.Y., dusted off Regan with a bean ball.

"Despite all the talk to the contrary it looks to me like the present administration is doing a better job of raising the deficit than Carter, or even, my God, Lyndon Johnson," he said.

Regan did not flinch.

"Dollar-wise you're right," he stammered. "We are not proud of these deficits. We do not want deficits."

Secretary of Defense Caspar W. Weinberger and Secretary of State George P. Shultz received warmer receptions. Both were given standing ovations when they began and ended their addresses.

Regan, Shultz and Weinberger, a favorite of conservatives because of his support of increased defense spending, were among six Cabinet members scheduled to appear at the three-day conference, the nation's most influential annual gathering of conservatives.

Coming at midterm in Reagan's presidency, this year's meeting is highly symbolic. It comes at a time when some conservatives are pressuring Reagan to announce his candidacy for reelection, while others, like New Right direct mail expert Richard Viguerie, are suggesting he has deserted the cause.

Reagan's approval rating among conservatives, who have long provided his base of support, stands at 56 percent, according to presidential pollster Richard Wirthlin.

The American Conservative Union and Young Americans for Freedom, sponsors of the conference, have long and close relationships with Reagan. Rep. Mickey Edwards (R-Okla.), ACU chairman, said he hopes the sessions will demonstrate that "some of the criticism directed against the administration by conservatives isn't widely shared."

But while Reagan remains popular among the 1,000 conservatives at the conference, a widespread uneasiness with many of the administration's policies and appointees has surfaced repeatedly. And, the president has come under a drumbeat of criticism from various conservative groups.

The loudest applause at Thursday's opening session, for example, came when House Republican Whip Rep. Trent Lott of Mississippi said, "I wish the president would surround himself in the White House with more people who helped him get elected in the first place."

Shultz encountered the same restlessness.

One questioner asked him about "selling out Taiwan."

Shultz replied, "We're not going to turn our backs" on the people of Taiwan who he claimed "fought on our side" during the Korean and Vietnam wars.

Shultz and Regan were also sharply questioned about administration moves to prop up the beleaguered International Monetary Fund, which many conservatives believe benefits only "the big banks."

Regan devoted a major portion of his speech to this issue, maintaining that the moves were necessary to maintain a strong export market for U.S. products. "I look at it as an insurance policy against the loss of jobs--insurance against catastrophic losses," he said, adding, "We are not bailing out the banks per se."

Weinberger urged that conservatives rally to support administration efforts "to rebuild America's defenses," arguing they are necessary to counter a massive arms buildup by the Soviet Union. "This is a not an easy course, or a popular one," he said.

Although Weinberger's remarks were greeted warmly, many conservatives expressed doubts about other administration spokesmen and the president.

"All of them are very smooth and very polite," said Jo Ann Long from North Carolina. "But I think Reagan has done us in. He told us one thing and he's done another."