Berlin's fun, cheap and is a moderate startup hub. You can't compare the startup activity here to the valley, but well, you can't compare the Valley's music and arts culture to Berlin's.
Plus, as has been mentioned here several times, you can't just up and go to SFO without the appropriate paperwork. You could spend three months there, but that's really more like an extended holiday than really moving.
As for English in Berlin, it's definitely doable. Socially I really find it worthwhile to put effort into learning German since otherwise you're often stuck being the odd-man-out when going out in a group or hanging out with other foreigners.