Silicon Valley is not know for it's breweries, but there are a few.
Tied House Cafe & Brewery - 954 Villa St, Mountain View, 94041 - (650) 965-2739
Tied House Cafe & Brewery - 65 N San Pedro St, San Jose, 95110 - (408) 295-2739
Faultline Brewing Company Restaurant - Pricey & not all that great
Plan on doing a bit of driving. Much better pubs are either up towards S.F. or on the east side. One I like that has great beers is The Bistro - 1001 B St, Hayward, 94541 - (510) 886-8525 There are a bunch of places around Berkeley.
http://www.ci.berkeley.ca.us/CoolThings/Other/breweries.html
Must visit is the Toronado in S.F. [
http://gear.toronado.com/draft.htm ] You can drive over to Hayward and take the BART in.
Toronado Barley Wine Festival 2007
Saturday February 17 to Saturday 24, 2006
Location: Toronado, 547 Haight, San Francisco, California
Time(s): 11:30 AM to 2:00 AM Daily
Regardless of what you have heard about California drivers, the reality is worse.