You can probably figure out a way to do it via public transit, but it would be convoluted. Take a car.

BTW, the reason that BART doesn't serve locales in San Matepo and Santa Clara County is that when the system was originally built, those counties (and Marin) opted not to pay the .5% sales tax required to join. The original vision of a system ringing the Bay was done in by local politics.

BTW you will be able to take BART from SFO in 1-2 (3? 4?) months but it won't go to Mountain View. A shame IMHO.