Blue Hop on Hop Off Tour Bus.. Located at Union Square 9am departures.. This has got to be the best way to Tour San Francisco and get off and explore and back on.. All for about $20.00 All day long till 5pm..I had a 2 day pass..First day took the tour..Hop off after the 2 hours and on again to where I wanted to explore.. off and on.. I saw everything.. Highly recommend Museum of Science and a must to walk Haight Ashbury.. Go shopping at Pier 39.. Wonderful narrative tour..