SFO is a 'liberal' city, but the idea the tech people are majority liberal as well needs a strong does of supporting evidence. My own observation is that much like the rest of the rest of the populace, it's a spectrum. I have talked to many SFO folks looking to move out of there specifically because they want to be somewhere 'conservative', usually using more colorful language.

And I also have some doubts about the whole 'techies are going to come here and take over' trope. Sure, they will influence things (money always does), but entrenched political and social structures don't just melt away overnight. They know the rules of the game because they made them. I live in a pretty lefty area that's also pretty desirable to live in, and periodically you'll get an influx of individuals from other places that make noise about some aspect of the area that isn't conservative enough for them (taxation, commonly) and how they're going to change things. And the incumbent political actors spin up and work the system and it usually goes nowhere. I suspect you'll see much more of that than radical changes brought on by the arrival of tech money.