I can't recommend Berlin enough, especially for building an MVP.
I don't get this obsession with moving to a startup hub before there's even most remote proof of your startup's viability. To me, it always raises the suspicion that one's less interested in actually building the business and more interested in living inside the movie The Social Network.
It's nice to be around people who value the things you value. It's nice to have friends you can talk to who understand what you are going through. I know for me, it's nice to be around people who are impressed when I do things that I feel are impressive, and it's nice to be around people who are better than I am.
I mean, yeah, there is a tech scene in davis and in sacramento... but it is a much 'smaller pond' - it really is pretty cool to be able to rub shoulders with the leading voices of your industry, and that's way easier to do here.
In a very real sense, you /can/ come rub shoulders with Van Gogh or Proust here, I mean, figuratively speaking. Many of the leading figures in the industry. Maybe you think wanting that is silly, but... yeah, some of us are really into that sort of thing.
I am in silicon valley, mostly for the social reasons you mention. I think that's valid, and it's worth the extra money for me. It's not worth the extra money for some other people, an that's fine too, but this is what I want to spend my money on, and I feel that I'm getting a reasonable value out of the deal.
(There is also monetary advantages... but if I'm being honest with myself, I'm mostly here for the social advantages.)
I've heard a wide range of stories - some claim speaking English exclusively doesn't pose any major obstacles. Others claim that knowing only English makes your life pretty rough.