Is it mandatory to get a prius to live in the bay area, CA?

I am going to San Francisco for a conference in December for a week, and will have lots of free time (I don't care about the conference so much, but since I am presenting my research, I can have it funded by my project and my wife and I need a vacation!). If I wanted to go to Napa Valley for a day trip is it easy to rent a Prius there? I don't think any car-rentals here rent Prii.