San Francisco is a terrific walking town. About 100 neighborhoods with walks in each one and walks linking them as well. Mostly weather cool enough to make the walk a pleasant warm up. Enjoy!
Don Diltz: Walk the entire lake for a 5 miler; the far south end for about 0.8. Birds, dogs, walkers, runners, bikers...lots of activity. On week ends, sometimes boaters. Golfing at multiple courses nearby.