For that, just divide yearly_salary by monthly_rent (for the same type/size of housing). You can also check crime data and other such things on http://www.city-data.com .

Many move from the Bay Area to Austin, Seattle, North Carolina, etc, especially when they're ready to buy a house. Unless something special is waiting for you, I'd say San Francisco will be a step down. I'd definitely recommend visiting first.

If you're moving for career reasons, then you should first see if the Bay Area company will allow remote working.

I've been there a number of times, but not for extended periods. I'm not moving, but the idea of moving has crossed my mind. I have no kids or family and I currently live downtown Austin in a studio (no car and bike everywhere without problems). I have a job at a local start up right now, but things change.