I will be carrying only 35mm equipment on this rip, so I will obviously look more touristy than someone wih a view camera. When I shot a few test pictures of a local fire station with my 4x5 Cambo several years ago, I'm pretty sure they thought I was setting up a rocket launcher. I got their permission before hand and they still came out to see what the heck I was planning to do. haha!
Anyway, I will be carrying a shoulder style gadget bag with two bodies and three lenses. I will also have a very light weight tripod and monopod that I may carry with me on occasion. I will be taking some infrared film with me which will need the tripod. I've heard that cops judge whether you're a pro versus amateur by whether you're carrying a tripod and they have apparently been known to enforce rules against commercial photography without a permit.
I remember hearing stories on the news about SF's terrible crime rate in the late 70s and still never really felt threatened, so I'm not anticipating too much trouble. My concern now has shifted to cops and security guards being the most likely interference. On a recent walking trip around Nashville, I wasn't harassed at all (even around the federal courthouse). I was almost hit by cars three times, though (and that's when I was in the crosswalk and the light sad "walk").