You probably want to take CalTrain to Mountain View rather drive up and down 101. It's awful at the best of times and right now it is covered in potholes so there is a non-zero chance that you'll end up hitting one and blowing a tire.

45-50 minutes if you get on an express. 1hr and 10 for the local trains. It'll take 47 minutes to drive if there is no traffic and anywhere from 1hr 20 to 2hr in rush hour.