Fillmore Jazz Festival is my second favorite street fair in San Francisco, beside Castro street fair (of course.) I guess it must be the crowd that not too young and crazy. Plus, the different stages of Jazz make me want to be in love... If you're around here, the festival starts 10AM till 6PM, on Fillmore between Jackson and Eddy street.
Updated: Myself at Fillmore Jazz Festival in front of Marc Jacobs store with a drink in my hand, as usual.