President Reagan will return to the White House this weekend, probably today, but it will be weeks before he resumes a full work schedule.

His return is welcomed by White House aides who do not find it coincidental that the administration's first serious setback on its economic program came while Reagan was recuperating in George Washington University Hospital from the March 30 assassination attempt.

While administration officials publicly questioned whether Reagan's presence in the White House would have stopped the Senate Budget Committee from turning down his budget, 12 to 8, Thursday night, there was a different assessment behind the scenes.

Noting that three conservatives bolted GOP ranks to provide the margin of rejection, a White House aide said: "It's hard for me to believe that a phone call from the president wouldn't have made the difference."

This comment foreshadowed a likely tug of war in the White House in coming weeks as Nancy Reagan and presidential aide Michael K. Deaver try to keep the president from rushing back into the political fray.

Hospital spokesman Dennis O'Leary told reporters at a White House briefing yesterday that the odds favor Reagan's coming home today but that no final determination would be made until he is X-rayed this morning.

A chest X-ray yesterday showed a translucent spot along the path of the bullet; Dr. O'Leary said it eventually will become scar tissue "but it's not quite there yet."

Doctors want to be sure that what O'Leary called "this little pocket" -- slightly less than a half inch in diameter -- is draining properly into the bronchial tubes and not getting larger. If the spot hasn't grown, O'Leary said, the president probably will be discharged today. If there is reason for concern that this morning's X-ray, more sophisticated X-rays will be taken.

"If those are all right, he'll probably still leave the hospital" today, O'Leary said. "If there's . . . any significant concern at all, we'll probably keep him until Sunday and get one more chest X-ray to evaluate it."

Even if the president does return to the White House today, he won't be rushing into a heavy work schedule. O'Leary cautiously told reporters that he thought the president could "handle" a television broadcast of maybe 10 minutes next week but that he wouldn't be returning to a half-day schedule in the Oval Office until the following week.

Deputy press secretary Larry Speakes said that "the president's doctors have emphasized to the senior staff that there should be a period of convalescence in which the president's schedule should be limited, and there will be no presidential travel for the next several weeks."

Speakes made this statement in formally announcing the indefinite postponement of a meeting with Mexican President Jose Lopez Portillo that had been scheduled for April 27-28 in Tijuana.

O'Leary said that the stress of traveling would not be desirable for the president at this time. He also said that Reagan would require a full night's sleep and perhaps afternoon naps during his convalescence.

While the total picture O'Leary painted was one of a healthy and physically active 70-year-old who had made a highly satisfactory recovery from a serious wound, there is concern at the White House that the pressure of political events will rush Reagan, whom Speakes has called the "super salesman" of the administration, into doing more than he should.

It is no secret that administration officials dealing with the budget think that the president is his own best asset in coaxing his economic program out of Congress. However, the half dozen dates proposed for a nationally televised presidential address on this subject include some in late May and one as late as June 1.

Reagan will probably speak to the nation long before then. But the relatively long-term contingency planning reflects the protective concern of Nancy Reagan and the related view of senior advisers that it would be a mistake to risk Reagan's health by pushing him too fast.

"The president has to be allowed to recover at the same pace that anyone else would recover," a political adviser said Thursday.

This concern was reinforced this week by the advice of two other prominent victims of gunshot wounds who visited the president in the hospital.

"Take it easy, Mr. President," advised Vernon Jordan, president of the National Urban League, returning a visit Reagan paid him in a New York hospital last summer.

And John B. Connally, who was governor of Texas in 1963 when he was wounded in the assassination of President John F. Kennedy, also advised Reagan to go slow.

"The only difference between our wounds is that I got hit in the right lung and you were hit in the left," a source quoted Connally as saying. He reportedly went on to tell the president that his recovery would take longer than he thinks.