Moving to the area soon and not sure about anything

I checked out the ultimate thread and most of it seemed more for SF proper than anything else, so I apologize if there's already answers to these questions.

23, got a job with Google, looking to move to the area from Chicago. Been trying to find apartments with a few other guys who are starting the same time I am, and it seems like the best deals I'm finding for apartments are in Sunnyvale, but they're apprehensive because they're not sure if lower rent = bad neighborhood.

Can someone tell me what the area is like (not just in terms of crime, but in general)? I've been trying to research it to not much luck, and I'm moving in a few weeks, so literally anything is appreciated.

Is the public transit service reliable enough as well? Coming from Chicago, I don't own a car, but just rely on the CTA to get me everywhere, and I've never had a problem with it, but my first impression of Caltran and the SJ Light Rail is that their service is comparatively sparse.

(edit) Thanks to everyone who has given advice so far, I really appreciate it!