Excitement - and a few complaints - in San Francisco

A fog-clearing heat wave and Geraldine Ferraro were generating the most excitement here as Democrats and the news media crowded into town for today's opening convention session.

The mood of visitors and hosts alike was charged with anticipation - Union Square, Fisherman's Wharf, and Ghirardelli Square merchants watched cable cars disgorge eager Democratic shoppers and delegates who wondered aloud what twists the Ferraro vice-presidential nomination will have on anticipated floor fights.

San Francisco's summer fog and chill here lifted over the weekend, bringing unusually crystal clear vistas of bay and city skyline north of convention headquarters. The warmth added to the festive spirit on streets decked with red, white, and blue bunting.

While Democrats seemed content with the setting of this week's convention, there were some rumblings of complaint. Jesse Jackson packed Union Square with ''rainbow coalition'' ralliers on Saturday, and despite conciliatory talk of forging party unity this week, he mentioned discontent with Walter Mondale's unilateral decision to oust Democratic Party chairman Charles Manatt and to offer Bert Lance, a controversial figure from the Carter administration, a leading role in the Mondale campaign. Jackson campaign staff said Mr. Jackson and Gary Hart should have been consulted.

Senator Hart, who arrived here Saturday, also condemned the move. His campaign manager said as many as 40 Mondale delegates had told the Hart camp they may protest by withholding their votes on the first ballot. There were rumblings that the Lance issue might be used as leverage among Hart and Jackson delegates in floor battles that may emerge.

Meanwhile, there was grousing by reporters and delegates about the low-slung arches of Moscone Center, which afford unobstructed views of the podium only for network TV anchormen and delegations seated front and center.

Police with riot gear ringed Moscone Center in a vigil that would last from the weekend through the convention, which winds up Thursday night. They were reinforced by helicopters buzzing overhead and concrete barricades surrounding the low-lying glass-and-steel convention center. Marches and demonstrations were aimed all week at the convention center, with yesterday's gay rights rally expected to draw 100,000 and a labor rally between 75,000 and 100,000.

Sign-carrying demonstrators were stationed at corners throughout the downtown area, and out-of-town Democrats had a hard time distinguishing protestors from striking retail clerks picketing two large department stores.

Caucuses and candidate entourages were staking out their headquarters at a knot of hotels around Union Square. Copy machines were being revved up as special-interest groups, Democratic Party officials, and campaign management began spewing out press releases for the 12,000 reporters expected. The Washington Post even has a media reporter here to report on the press.

On Saturday, workmen were still hammering on the red, white, and blue podium as a band and military honor guard practiced for the convention opening. Technicians were busy rotating colored spotlights that will ultimately focus on the party's nominee this week.

Locals noticed the change in atmosphere around town with some satisfaction.

''The sales people are bending over backwards to be helpful to visitors. We won't tell them we're locals,'' said Diane Sprouse, a convention volunteer from nearby Concord, Calif. ''You can tell who the tourists are, because they're looking up at the skyscrapers and they're dressed for sunny weather (which isn't normal in summer here).''

Hotel space didn't seem as tight as expected, even though 30,000 visitors ultimately will be here for the convention. Dottie Moss, who has no connection with the convention, arrived in town and was easily able to secure a room at the exclusive Stanford Court Hotel. She said the ''excitement in the air'' was enough to make up for the long wait for a cable-car ride and the crowded streets. She said she thought the excitement was centered on the ''monumental breakthrough of a woman for vice-president.'' Asked if the excitement had gripped her too, Mrs. Moss said, ''a woman's not enough'' for her to vote for a Mondale ticket.

Official celebrations were kicked off yesterday by a mass reception at City Hall, sponsored by Mayor Dianne Feinstein and by a bay-front party given by California's most powerful Democrat, Assembly Speaker Willie Brown. Each state delegation will be given a reception in private homes.

One mustachioed salesman who had set up his campaign-button display on the steps of an abandoned storefront near Moscone Center made one of the most interesting observations of the weekend. With an overabundance of Jesse Jackson, Gary Hart, and Walter Mondale buttons on the table, he named the hottest-selling items. ''Reagan-Bush. They're sold out.''