The royal horseback ride--a long-awaited feature of Queen Elizabeth II's introduction to California chic--is out Tuesday, but President Reagan's barbecue lunch for her at his mountaintop ranch survived schedule changes brought about by California's worst storm of the year.

The White House announced tonight that Reagan will welcome the queen at Santa Barbara airport Tuesday morning when she and Prince Philip arrive from Long Beach for the day. Originally, plans called for them to steam into Santa Barbara harbor on the HMY Britannia. But heavy rains, strong winds and rough seas, which beat the California coastline throughout the day, finally forced a change in the plans.

Sunday night, the queen met First Lady Nancy Reagan in California for the first time at a star-studded gala Hollywood dinner in the queen's honor. Today, in a speech at City Hall, the queen thanked Americans for their support in the Falkland Islands war.

"The support of your government and the American people touched us deeply and demonstrated to the world that our close relationship is based on our shared commitment to the same values," she said.

The queen noted that her journey north along California's coast had been made about 400 years earlier by Sir Francis Drake. He claimed the territory as "Nova Albion" for the first Queen Elizabeth and "for the queen's successors forever."

"I am happy though to give you an immediate assurance, Mr. Mayor, that I have not come here today to press that claim," she said.

About 1,000 people, including about 100 protesters, gathered on the soggy lawn south of City Hall and greeted the monarch with cheers and boos as she emerged with Mayor Tom Bradley. The queen passed only 70 yards from the crowd, well within hearing range, but continued to smile and wave until she boarded a limousine for a luncheon at the Los Angeles Music Center.

President Reagan flew to California today to be on hand in Santa Barbara Tuesday to welcome her.

The White House said the queen would fly from Los Angeles to Santa Barbara instead of taking the Britannia. But a British Embassy spokesman said the yacht would leave as planned at midnight, but might dock somewhere else.

Another problem had been how to get the queen to the Reagan ranch, since parts of the road become impassable in heavy rains. One solution under consideration was putting the queen in a four-wheel drive vehicle, since she never travels by helicopter.

During a day of visiting civic landmarks around the city, the queen and Prince Philip toured a Rockwell International space shuttle facility where they tried out a shuttle flight simulator. Tonight they were to hold a dinner aboard the Britannia for an eclectic group that included community and business leaders. In addition, going aboard the sleek blue yacht were film director Francis Coppola, oil magnate Armand Hammer, astronomer Carl Sagan, Los Angeles Dodgers President Peter O'Malley, Bob Hope, Walter and Lee Annenberg and Frank Sinatra.

The rain was no show-stopper last night, though some Hollywood royalty dripped with more than diamonds. After weeks of wondering whether to curtsy or not curtsy, to speak or be spoken to, their dilemma was resolved for them. Gawking glitterati caught little more than a glimpse of the queen. She and Prince Philip, accompanied by Nancy Reagan and the royal party, walked along a red carpet to an enclosed reception area where the Los Angeles businessmen who underwrote the party's business expenses, with their wives, were the only guests. From there, the queen went directly to the head table; only the people there got to shake her hand. Most of the women curtsied, and the men bowed.

The queen's dress had a white chiffon skirt and a bodice embroidered with California poppies, a salute to the state she was visiting. At her throat was a three-strand diamond necklace.

"I'm probably the only person in California who knows that that poppy is spelled Eschscholzia Californica," said Hardy Amies, who designed the dress.

Nancy Reagan's dress was a purple Galanos with gold threads and gold leaf costume jewelry. Among the approximately 500 guests, designer originals were standard. There were some other fashion standouts, however: Patti Davis, one of three Reagan children present, wore a full cotton skirt and boots; Roy Rogers wore his cowboy outfit but left Trigger home; Rod Stewart wore black leather pants and gold shoes and his wife Alana a mini-skirt to match.

Stewart and nearly two dozen other British stars were seated at the head table with the queen in a transformed Stage 9 at 20th Century-Fox, where the walls were adorned with a backdrop from the movie "From the Terrace" and where Shirley Temple filmed "Stowaway" (1936), Tyrone Power "The Razor's Edge" (1946), and Marilyn Monroe "The Seven-Year Itch" (1955). From 1972 to mid-January of this year it was the set for "M*A*S*H".

On the queen's left was British producer/director Tony Richardson and on her right, wealthy Los Angeles businessman and Reagan kitchen-cabinet member Holmes Tuttle, who organized the evening's host committee.

"Everybody here was worried about the image of the Reagans hobnobbing with the queen," remarked one British guest over chicken pot pie and toasted coconut snowball ice cream. "Well, what about the queen hobnobbing with these millionaires? It's cost-effective efficiency. She can do more in a week for British trade than Margaret Thatcher can in a month."

Sahl said he was ready if the queen wanted to get away from small talk.

"I'm going to tell her I read what Paul Volcker said. This experiment has failed. I want to know if she'll take us back," said the comedian.

Holmes Tuttle didn't let ceremony stand in his way. "You were told not to talk to her unless she talked first," Tuttle said. "But Lee Annenberg said don't bother with that, just talk to her as you would anyone else. We got along great."

Sinatra produced the entertainment, dusting off the White House gig he and Perry Como performed for Italy's president last year. Dionne Warwick shared the billing as did Ed McMahon, who turned out to be the first of the tour to use the "fit for a queen" line that no good royal visit could end without.

The slightly off-color jokes of George Burns, 87, kept 500 pairs of eyes glancing sideways to see how the queen reacted.

"If a director wants me to cry, I think of my sex life. If he wants me to laugh, I think of my sex life. I must be a great actor," said Burns, "because this morning after taking a shower, I took a look at myself and I laughed and cried at the same time."

Also: "There isn't a thing I can't do now that I did when I was 18. Which gives you an idea of how pathetic I was at 18," Burns said between cigar puffs.

Julie Andrews, who sat beside Prince Philip, said later she was sure the queen loved it. Tuttle said he had a couple of anxious moments until Burns "started to sing and then everything went all right."

Except for a long head table, guests were seated at round tables, distant and no doubt indistinguishable from the queen's vantage point.

"A bit dour, wasn't it?" Julie Andrews commented to her husband, director Blake Edwards, as they were leaving the party. "Too bad they didn't have all the great stars seated in one place so the queen could see them."

Among the throng: June Allyson, Fred Astaire, Michael Caine, Richard Chamberlain, Lynn Redgrave, Joan Collins, Buddy Ebsen, Samantha Eggar, Greer Garson, Glenn Ford, Irene Dunne, Anthony Hopkins, Elton John, Gene Kelly, Jean Marsh, James Mason, George Murphy, Ginger Rogers, Danny Thomas, Robert Wagner, Henry Winkler and Loretta Young.

Others included British Foreign Secretary Francis Pym, Henry Kissinger and assorted state and local officials including Sen. Pete Wilson with his companion, Gayle Graham.

Before dinner, everybody jammed into a cocktail party at the other end of the cavernous sound stage where the decor included a statue of Bacchus from the film, "The Robe."

The faces in the crowd were straight out of the movies, as hotel man John Bennett Coleman succinctly put it. There was Bette Davis holding court against one wall, watched over by Roddy McDowall and James Mason. Loretta Young was surrounded by admirers. Fred MacMurray, Glenn Ford, Robert Stack, Gene Kelly, Charlton Heston, George Murphy were but a few who drifted out of the past.

"George," said one woman to her husband, "Bette Davis is here, to heck with the queen."

"She's our queen," said McDowall, who added he knew all of Davis' films "chapter and verse."

Davis herself said she had never met any royalty. And why was that?

"It wasn't up to me to arrange it."

Mort Sahl played the evening's court jester, providing some comic relief in the 70-plus degree temperature.

"If former Argentine president Leopoldo Galtieri had had a better year," Sahl said referring to the Falklands, "we'd be having dinner with him. So I'm glad she won. She should be glad Reagan won. It's a nicer party. Artists aren't famous for their parties."

AFI director George Stevens Jr. was at least one Washingtonian there grateful for small favors. "Isn't it nice to go to a dinner you don't have to pay $300 to go to."

"I'm so excited I can't stand it, Dahling," Eva Gabor told one guest. A little later she confessed, "I can't for the life of me remember names. That's why Dahling came into fashion--you can't hurt anybody calling them Dahling."

Elton John, flashing a diamond brooch on his suit lapel and another diamond in one ear lobe, said the last time he saw the queen they danced to "Rock Around the Clock." It was at Prince Andrew's 21st birthday at Windsor Castle and as dancers go, "She's good. It was the highlight of my life."

Roy Rogers, there with his life's companion Dale Evans, said he almost didn't come because "parties scare me to death. I'm kind of like the old Indian. I gotta walk 10 miles in the old moccasins before I know the person. It's hard for me to talk."

Maureen Reagan said she and her husband had just spent a couple of days at the White House. She said she asked her father if he were going to run again and told him she hoped he would.

"And with that benign smile of his he said, 'Duly noted.' "