If you’re going to VMworld and staying in the Hilton, don’t rely on Google Maps for directions. It thinks that 333 O’Farrell St. is Redwood Alley. Instead, the hotel is actually very close to the Powell St. BART station, making transit to the hotel cheap from SFO ($5.15 rather than a $40 cab ride).
This is actually where you want to go (if you can’t see the map use this link instead):
If you’re interested in taking the BART take the Dublin/Pleasanton train to Powell St. Takes about 30 minutes and is way cheaper than a cab. I made a sample schedule for myself at www.bart.gov.