In his televised address to the nation on Aug. 16, President Reagan said a "sound and lasting economic recovery" could only be achieved slowly without any "sudden boom or upsurge."

Now, buoyed by a week of cheering economic news and the familiar surroundings of California, Reagan's natural optimism appears to be reasserting itself. While no one is saying so directly, it is clear that Reagan and his principal spokesmen now believe the long-predicted recovery is at hand and will last until Election Day and beyond.

Last week, after passage of the administration's $98.3 billion tax bill, White House chief of staff James A. Baker III predicted a long-term drop in interest rates. Today, White House deputy press secretary Larry Speakes termed the interest rate decline "remarkable," and said it would lead to a reduction in home mortgage rates and a continued reduction of the rate of inflation.

According to some who have discussed the economy recently with Reagan, the president is even more bullish on the American economy in private than his spokesmen are in their public statements.

"The president was an optimist when everything looked bad to the rest of them," one administration source said. "Now he really believes that the recovery is at hand."

Some of that optimism was apparent Monday at a $1,000-a-person fund-raiser for Republican Senate candidate Pete Wilson. Dressed in western garb and speaking from a Twentieth Century-Fox sound stage, Reagan gave a glowing account of what he considers the central achievements of his administration: lowering of the inflation rate, reducing income tax rates and building up U.S. military capability.

To the surprise of some in the audience, at a time when unemployment is about 9 percent, Reagan even quoted himself approvingly as saying during the 1980 campaign that, "Recession is when your neighbor lost his job, a depression when you lose yours and recovery was when Jimmy Carter loses his." In retelling the story Monday night, Reagan did not identify Carter by name, referring to him only as "the incumbent."

While Reagan is clearly in a good mood these days, his speech was a disappointment to some key backers of San Diego Mayor Wilson, who faces a difficult campaign against Democratic Gov. Edmund G. (Jerry) Brown Jr.

The president rarely mentioned Wilson at all, and at one point seemed to have forgotten that Wilson was running for the Senate instead of for governor.

After saying his administration's "New Federalism" proposals would return government to the levels "closest to the people," Reagan added, "Now, who would you like to have in California helping administer that switch back to that kind of federalism?"

Informed administration sources said the president discarded a draft speech prepared by his political office that extolled the San Diego mayor, who last week opposed the Reagan tax bill while Brown supported it.

Wilson's opposition reportedly irked the president, who remembers that in 1976 Wilson campaigned for President Ford against Reagan in the crucial New Hampshire primary.

"He didn't want to be hypocritical and praise Pete to the skies, so he threw the draft away and just winged it," one official said.

Whatever else the speech lacked, Reagan succeeded in his attempt to avoid hypocrisy. His appeal for Wilson was based on the two reasons the White House supports the San Diego mayor: a desire to keep the Senate in Reublican hands and personal distaste for Brown, who succeeded Reagan as governor in 1975.

In addition to his reservations about Wilson, the speech also suffered from Reagan's unconcealed desire to spend as much of his time as possible at his mountaintop ranch northwest of Santa Barbara.

"He feels he's worked hard, is entitled to a vacation and is going to take one, said one source close to the president.

Tonight, at a reception for Republican gubernatorial nominee George Deukmejian, Reagan was asked what part of the job of being president had proved surprising to him.

"It's kind of hard to answer," he replied. "I'm enjoying myself."

In contrast to his mood the previous night, Reagan was clearly enthusiastic about Deukmejian, who played an important role as a state senator during the Reagan governorship in pushing tough anti-crime measures. Reagan said that "the problem of crime is on people's minds," and praised Deukmejian as an effective and experienced leader.

The president also reiterated his intention to reject any appropriations bills that exceed previously authorized budgetary limits, saying to loud applause: "I have promised in writing that I will veto budget-busting bills."

Today Reagan visited the Los Angeles office of Dr. Howard House for an ear examination. Reagan is hard of hearing, but the White House said the visit was so routine that the doctor had notified him of the appointment by postcard.