I spent for three months every winter in silicon valley without a car. I know the bus is available to Google at Charleston; VTA #40, one in every hour. The bus stop is located in front of Google Building 43. You dont have to walk about 1.5 miles.
From Mountain View #34 goes to San Antonio Transit Center to change to #40:
However the availability of #34 is five buses in a day. If you come from San Francisco, you may walk about 1/2 mile from Cal Train San Antonio station to VTA Bus Transit at the shopping center for your short cut to catch #40.
The following is the VTA route map. VTA is a good public transportation system in valley, particularly Light Rail is great.
Google to Mountain View is just about 2 miles; I walked one time after the meetup late at night.
Edited: 4:29 am, November 20, 2012