Do you live in San Francisco or travel there a lot? Need to know what kind of shoes to wear...?

It depends in part on what you plan to do, because people do dress up to go to bars and restaurants (not super-high heels, they don't work on steep streets unless you plan just to get in and out of a taxi or limo). For just hanging around and sightseeing, athletic shoes and closed-toed casual shoes are the most popular. No flip-flops, and a minimum of sandals, because SF is not Southern California -- it is colder and more formal.