Alcatraz is cool, and it's also a short trip. We took the boat over at 4pm and were back as the sun set, in time for dinner. It's just a boat ride, a short tour, and then you go...nothing else to do there. So, you might as well see it. it's the only thing I saw officially in San Fran. The rest of the time I visited with people or bummed around Chinatown and the Italian neighborhood (forgot its name).