I actually had a similar experience. Spent most of my life in SF but lived for about 6 months in Manhattan. It was far, far easier to meet women. In fact, a guy can even be a bit of a wallflower and still meet women in Manhattan, because they will take the initiative. Funny, up to that point, I thought SF was a pretty good place to meet women, because my only point of comparison was San Diego, which is a pretty rough dating scene for men. I actually still think SF is ok, because it has a greater concentration of jobs that appeal to women, as opposed to the valley. But it's no manhattan (I suspect that nowhere else in the world really compares).
You know, this is actually one of the benefits of being in a city where tech isn't the main industry. New York is a far bigger center than SF for fashion, publishing, advertising, and so forth - fields that attract more women than men.
San Diego isn't that rough; it's only rough if you aren't in the "scene". That said, if it isn't your thing, then I could see why it wouldn't work out - Las Vegas was rough for me because my personality didn't fit in with the "scene" there.
Having lived on the east coast, midwest, and west coast, I would say the resources are certainly different at a business level (capital, talent, etc) although you can certainly make do wherever you go.
However, anyone who thinks there are hot girls in SF has never left SF.
