Anecdotally, I've been here 30 years and never victim of a "dangerous" crime. Fat chance you move to Mountain View to work at Google and anything happens to you.
The only place in CA someone reading a "Best City for Techies" will encounter crime is Market St. and Tenderloin in SF. The rest of it in deep Oakland, Stockton, Modesto, San Bernardino, and pockets of LA, they will never end up.