I've never had a problem with a tripod on sidewalks. All in all, with iPhones and Holgas and tourists and a big 'Art' school downtown, you can do most anything. I've seen students shooting films laying dolly tracks all over the place with people just going around. Don't block the full sidewalk, watch for people in wheelchairs and such, and keep an eye on dogs mistaking a tripod leg for a tree.
Speaking of which, keep your eye out for dog poop.
And watch for bicyclists and cars. I'm not sure which is worse- cars do more damage, but there are more bicyclists doing dangerous moves. Just approach any intersection as if you are playing Asteroids- flying objects can come from any direction at any moment. DO NOT blindly trust things like 'WALK' signs and traffic lights. Too many people take them as mere suggestions.
Not sure when you were last here. SOMA has changed a lot in the last few years ('South Beach' is simply a real estate creation, still SOMA). Valencia Street and Dolores Park have a lot of life, albeit a rather narrow 'ecological niche.' Walking Market St. to Haight, up to Glass Key for some film (and music), over to Divisadero and then down the Panhandle to the Park or Upper Haight (Haight-Ashbury) would be a nice stroll. Crissy Field in the Presidio has become quite a nice promenade. Starting at the end of the Fishermen's Wharf tourist area, the National Maritime Museum's ship collection at Aquatic Park is nice, Fort Mason has a great community garden tucked into the middle of the upper area, the walk to the Palace of Fine Arts (recently restored, with Barn Owls just fledging) and along the Marina Green and Crissy Field is nice, and Fort Point under the Golden Gate Bridge is a great building and location.