Looking at google maps, the mountain view location seems right off the street and does not seem to have a fence, so you can probably go into the front door or ring the bell and ask for an interview.

However are you actually asking if anyone will interview you if you just walk in off the street? I would be extremely surprised if anyone would be granted an interview without an appointment. I certainly would not.

In the past several people have done this I have know of at least four, they got the interview but no success story of getting in, best of luck.