Travel around using public transportation. Which places are convenient to get from/to, and which places aren't?

Google Maps is a pretty good simulator for this.

One thing to keep in mind, if you're coming from somewhere with marginally sensible public transit, like New York City or Portland: The Bay Area is not a metropolitan area; it's several metropolitan areas that don't cooperate very well. Bus systems are on the city or county level (Muni, ACTransit, VTA, and SamTrans); there are light rail systems that don't connect (BART and VTA), and a commuter rail line that doesn't reliably sync with the above (Caltrain).

Visit the offices of the major tech companies like Google, Facebook, Apple, and Twitter. Ask some of their employees how they feel about being a software engineer in Silicon Valley.

Find a current employee to give you a tour. You generally can't wander around people's offices unescorted.

Eat at local restaurants - not so much the fancy/expensive ones, but the ones a person might go to for a typical, everyday lunch outing.

The larger companies have cafeterias; even many startups have catered food.

See some of the sights. Again, the emphasis would be on the things that would affect our everyday lifestyle, should be decide to move, not so much on the tourist attractions. For example, the Golden Gate Bridge is an awesome structure, but I doubt it would improve my everyday life very much. In contrast, living near a good running trail would be a big boost to my lifestyle.

Look up bike trails and such online.

Do some apartment viewing, to get a feel for how much rent a good/medium/student apartment costs in different areas and how good the amenities are.

Expect to be astonished by the prices, and watch out for aggressive HOAs.

Go to some local LW meetups, if there are any scheduled for the time window.

Subscribe to the bayarealesswrong mailing list on Google Groups; meetup announcements are posted there.

Visit the Stanford and UC Berkeley campuses and the surrounding areas.

Go for it. Stanford is huge and Berkeley is hilly, by the way.

Interact with locals and ask them about their experience living in the region

See also mailing list. Also note that the visible populace of a busy town looks very different at different times, based on whether people are at work, whether school is in session, etc.

Visit a number of different neighborhoods, to try to get a sense of the pros and cons of each

You could spend days or weeks doing this in one town. Live near where you work, or find a workplace that's near where you want to live — commuting sucks.

Discuss how to apply Bayesian decision theory to the problem of finding the optimal place to live ;)

Hmm ....