At the height of San Francisco's tourist season, workers struck 12 of the city's most expensive hotels, and more than one-third of the police officers in Mobile, Ala., joined firefighters on picket lines in a growing municipal strike.

In other labor developments, preparations were made for a possible strike by film and television actors, and tentative contract agreements were reached in disputes involving an orchestra in Cleveland and a newspaper in Denver.

San Francisco hotel guests carried their bags and settled for sandwiches instead of regular meals. Two hotels said they would shut down. The striking union represents some 6,000 chambermaids, bellhops, clerks and restaurant workers.

Of Mobile's 1,788 city employes, about 1,000 belong to unions. Unions for municipal mechanics, electricians and carpenters planned a meeting Friday to decide on joining the walkout.

The Screen Actors Guild and the American Federation of Television and Radio Artists, negotiating jointly for the first time, represent 90,000 actors. They demand a 40 percent pay increase plus a percentage of the producers' gross in the pay TV market.

The Cleveland Orchestra agreement, ending a two-week strike, will increase the minimum weekly salary for musicians to $610 by 1982 from the present $450.

The Rocky Mountain News and the Denver Newspaper Guild reached a tentative settlement after 10 months of contract talks. The proposed three-year pact would provide an average pay raise of 7.6 percent the first year and increased company pension and health insurance contributions.