"If SF weren't such a liberal city, it would have far fewer homeless."Sorry, but that's an argument that you have to prove, with actual facts. You can't simply assert your worldview to be true.
Could the homelessness problem in SF be caused by excessive social services? Sure, I suppose it could. But it could also easily be caused by the incredibly moderate weather (which makes it possible to live on the streets year-round, without fear of freezing to death -- many cities with moderate climates have similar problems). Or, for that matter, the homelessness problem could be due to the absolutely insane cost of living, and a lack of social services.
I don't know the cause of the problem, but I'd still wager that it's a bit more complicated than a simple-minded theory involving the politics of the city government. I also question the premise of any theory that assumes that the homeless and mentally ill (neither of whom are highly mobile populations) are packing up and heading west explicitly to take advantage of the "liberal" social services in San Francisco.