If you are already in the Bay Area, I would recommend that you probably just stay there unless you don't plan on raising VC. It's certainly not the only place you can start a company, but it is still one of the best places to do it.
In general, the early parts of any startup can be achieved pretty much anywhere. Building product, early customer discovery, marketing, etc. are not really dependent on geography for a large number of tech-focused startups.
Location becomes an issue when:
* you have some physical presence as part of your product (e.g. meal delivery, bike shares)
* you need to hire (unless you a comfortable with remote work)
* you need to build partnerships
* you need to visit clients (this can be solved by being near a major airport)
* you need to raise capital (the terms and availability are typically just a lot better in the bay area and a few other big VC markets)
So yea, if you are in the Bay Area already and you are wanting to build a true, hyper-growth startup, I would suggest that you just stay put since it will be advantageous further down the line.
