The Best Day in San Francisco
I've lived here for seven years. Bay to Breakers is without a doubt the best day of the year in San Francisco, every single year. It is the perfect crystalization of what it means to be San Francisco. A hundred thousand people come out to Have Fun. Period, end of story. B2B is better than Alcatraz, The Golden Gate Bridge, Chinatown, the cable cars, Fisherman's Wharf (yikes), the Blue Angels, and Golden Gate Park, COMBINED! (Well, B2B has Golden Gate Park in it, so that's cheating).
If you enjoy fun, you will make sure that your visit to the city puts you at Embarcadero and Howard at about 7:30am on the third Sunday in May.