Some entertaining notes: its a city that can change very quickly in only a few blocks.
From "The Financial District", (Transamerica building, among others) a few blocks' walk west along Market street (streetcars, no left turns) takes you to 'Union Square', a shopping mecca, and a few blocks further you're into a bit of a red-light district. There are homeless people everywhere, trash on the streets, etc; both north and south there's a lot of drug sales (the words 'The Tenderloin' should engender fear in your characters); when you reach city hall, though a gorgeous building, the surroundings near it are ugly and underwhelming. But just on the opposite side (now crossing Van Ness) are the concert halls and playhouses, with valet parking, etc. Travelling north up Van Ness you will find a bunch of car dealerships, hotels, and movie theaters.
Traditional tourist spots such as Lombard Street, Alcatraz, and the Golden Gate Bridge don't actually enter the denizen's lives too frequently; they are 'out of the way' of an average citizen, and a bit of traffic hazards. (Housing north of the Golden Gate Bridge, in Marin County, is much cheaper than housing in the city.)
For cultural diversity, Chinatown is pretty amazing; another culture shock can be had in the Mission district, which is primarily Latin; your Spanish speakers will get some good work there. Laundromats in the Mission are full of traditional household mothers with their girl children, but the streets are b
Haight Street (well to the western side of the city) may be a 'hippie' mecca, but it will also include a large number of youths. Its got a very diverse shopping district, from leather toys to hip clothing to tattoos and piercings to vintage; also some of the best variety of decently priced restaurants in the city. If your character's go to a bar in the Haight, let it be 'Hobson's Choice', a red building, dark-lit interior, crowded and exuberant (but never smoky - smoking is not permitted in California bars and restaurants)
Politics in the city are extremely liberal: the police aren't allowed to do much about the homeless problem because any proposed solution isn't "humane" enough; drug users are defined not to be the police focus, although they can and do go after importers.
In fact, unlike most California cities, there is very little freeway penetration: it is always voted down, and even rebuilding the portions of the freeway which collapsed in the 1989 quake has been prevented; car access around town is by surface street only, for the most part. There are, in fact, portions of the old freeway which are still standing, with an abrupt crumbled edge that marks where it collapsed: this would make a great backdrop for a battle.
Chinese New Year's feels like a city holiday, with a fantastic parade, and the Chinese love setting off (illegal) fireworks. The Gay Pride Parade is even more astounding for cultural conservatives, but is basically adopted by the youth of the city as an excuse to go party. Also, because the city is so surrounded by water, its a great place to go to view (legal) fireworks on American New Year's day, and again literally thousands of people show up to party in the streets with little legal enforcement. There is a bit of a U.S. Navy presence in town - the girls in the party will insist on getting out for Fleet Week, as thousands of sailors take to the streets and the Blue Angels entertain overhead. The 'Bay to Breakers' race is another excuse to have a large street party, as more people turn out to drink, dance, and party along the race route than actually run in the event.
Public transit: the "Muni" buses run everywhere - slowly. The old trolleys are primarily for tourists, but run up some of the steepest hills in town (north of Union Square). There's an underground - as mentioned above, the N-Judah connects the western extremes, such as the Haight, with downtown, including stops at City Hall, Union Square, and 'the Embarcadero' (financial district). It then turns south to go to the baseball stadium and Caltrain stop. There's also a surface streetcar, which runs along Market from the west, and then down Market past all of the same stops, then turns north through the Fisherman's Wharf section. (I kept writing Worf - too much star trek?) BART (Bay Area Rapid Transit) connects from San Francisco Airport (about ten miles south of the city, Millbrae area) through the Mission district (24th and 16th streets) and then along the City Hall (Van Ness and Market, near 9th street), Union Square (5th street), and Embarcadero (past the end of the numbered streets), then heads under the bay to Oakland and points on that side of the bay. One can transfer from BART to the underground without ever leaving the stations. Caltrain runs from about the baseball stadium south, through Millbrae/SFO, Burlingame, San Mateo, Redwood City, Palo Alto, and then off into Silicon Valley, terminating at San Jose. There are also Ferrys that leave from Embarcadero (the Ferry Building) to points north, east, and south on the Bay.
The Bay Bridge, a great metal structure, runs east from the city to Oakland; the only freeway penetration takes the 101 north into the city, and then east as it becomes the 80 and crosses the Bridge. Interestingly, the pilings for the Bay Bridge did not get driven into solid rock: the entire structure is anchored in the mud at the bottom of the Bay! In 'the Big One', that structure is coming down, as is much of the city (east of the Caltrain Station, the land under the ballpark, the Embarcadero, and even parts of the Financial District is landfill, which will be very bad for the buildings on top of it...) There is work on completely building a new Bay Bridge, which nearly paralells the existing one (and in fact, will use the same tunnel on Angel Island) - anybody driving along the Bay Bridge can see the work on the new one, one of the largest engineering undertakings we've made in this century. Earthquake or interference with that construction could provide entertaining plot hook.
On the water, there are always container ships: Oakland and Alameda on the east side of the bay are tremendous ports, including the largest container-ship cranes in the world (when they were imported, at low tide, they cleared the Bay Bridge by just under two feet - that might be another thing you could play with).
Angel Island (off the coast of Marin, east of the Golden Gate Bridge) is a beautiful and limited campground; although a number of people will be there during the day, at night the island reduces to about twenty campers and two park wardens, which might make it an interesting rendevous-in-the-dark point for somebody.
There's a restaurant atop one of the hotels (56th floor or so), which slowly revolves, giving panoramic views of the city and bay beneath, a great high-class meeting point or launching point for an aerial adventure. Let your characters be shocked at the $10 price for a cocktail, and tell them the menu doesn't list prices.
