Twenty-three conservative Republican senators expressed reservations about recent administration decisions to President Reagan yesterday, with Secretary of State George P. Shultz a chief target of their complaints.

Sen. James A. McClure (R-Idaho), chairman of the Senate Republican Steering Committee, called the 75-minute meeting with Reagan in the Oval Office "useful and positive, rather than a gripe session."

But other participants said senators were outspoken about the budget, Reagan's decision to comply with limits of the unratified SALT II treaty and what some senators said was an "ideological purge" of conservatives in the State Department.

One senator also complained of a "purge" of conservatives in the Office of Personnel Management since its former director, Donald J. Devine, withdrew his nomination for a second term, sources said.

Sen. Steve Symms (R-Idaho), one of the most outspoken critics of Reagan's decision Monday to comply with SALT II, said the exchange with the president was "very frank," especially regarding State Department appointments.

"We're his best friends in the Senate," Symms said. "After what he heard today, the president shouldn't be surprised if some of the State Department appointments run into opposition."

Sen. Jesse Helms (R-N.C.) and Sen. Orrin G. Hatch (R-Utah) complained about the rumored ouster of John A. Gavin, a political appointee, as ambassador to Mexico. The president, according to one person who attended the meeting, did not back down on any issue or appointment and told the senators that no decision had been made to remove Gavin.

Shultz has been a target of Helms for insisting on the nomination of career officer Rozanne L. Ridgway as assistant secretary of state for European and Candian Affairs, which Reagan did Tuesday. She is now ambassador to East Germany.

Helms reportedly said he would hold up the appointment of John D. Negroponte, the ambassador to Honduras, who has been named assistant secretary of state for scientific and environmental affairs, until James L. Malone, the man Negroponte would replace, is given another assignment. Malone is strongly backed by conservatives.

Sources said Reagan spent "most of the time listening," but did offer a general rebuttal to the suggestion that he has strayed from conservative objectives. Referring to his experiences as California governor, he said some conservatives "preferred to go off the cliff with all flags flying." Reagan said he prefers to get part of what he is after and come back for more next year.

McClure said that about half of the meeting was spent on budget issues and that he and others urged the president to "step up the tempo" and put more pressure on Congress for a budget bill.

"I think in response to our request he has pulled the budget very much to the front of the stove," "I think he will include it in his conversations with the American public."

Meanwhile, the House-Senate conference on deficit reduction encountered trouble in its second day as bargainers put aside Social Security, defense and other major issues dividing them but failed to agree even on lesser matters such as user fees and funding for the Strategic Petroleum Reserve.

"I'm not so sure we're going to be able to get a real budget," Senate Budget Committee Chairman Pete V. Domenici (R-N.M.) said, although several other negotiators said the shadow-boxing is probably necessary before conferees get down to serious business.

Some conferees said they would be lucky to finish before June 28, when the Fourth of July recess is to start.

House conferees would not back a Senate proposal to impose user fees for various government credit programs involving home mortgages, farm loans and student aid.

They also balked at a Senate proposal to stop filling the petroleum reserve, and senators rejected a split-the-difference House compromise. In addition, the two sides bogged down on enforcement procedures to guarantee enactment of proposed spending cuts.