While it's tempting to refer to the "San Francisco Bay Area" as a single cultural/economic entity, it really isn't. The male/female ratios will vary considerably within this region, along with the economic base.
I read an article a while back (which I could remember the link) that pointed out that as you move from south to north (ie., from southbay/San Jose to San Francisco), you gradually move from engineering/hard science to software to UI design to marketing/PR. There are major, substantial exceptions, of course, but as a general trend, I think it holds true.
As you move from South to North on this continuum, the male/female ratio changes substantially as well. Obviously, the PR, advertising, and design firms in SF have a lot of women working at them. Law firms, especially the ones that are not patent-law oriented, also have a lot of women - as paralegals, secretaries, and lawyers. I'd also guess that there are more fashion/interior decorating type firms in SF than in San Jose (it's not New York, of course, but insofar as the Bay Area has an industry, it'll largely be in SF). SF does have tech/software companies, though I've heard (I can't support this, it's just conjecture) that they tend to be less hardcore tech than the peninsula. The mission bay campus of UCSF may bring a lot of biotech folks to SF - not sure how that will influence things.
I've lived in SF, LA, San Diego, and New York. Because I grew up in SF, I don't have as good a sense of what it's like trying to "meet women", since I already had a large social network from high school and so forth. New York was the best (Manhattan) - girls would actually initiate conversations and give me their phone number. LA has lots of beautiful women, and it's a pretty good scene, but some (not all) women seemed to lose interest when they learned I wasn't a part of the entertainment industry (well, I was doing software for post production, but that counts as outside...)
San Diego was the absolute worst - the ratio of men to women was so high, and the men were so aggressive, that the women seemed to almost shut down and go into a shell. I learned something here - women don't seem to have as good a time when the ratio gets too favorable for them. It's surprising, but it makes sense. Women actually do like to pursue men, but if they're surrounded by a 3-1 ratio of men to women, and the men are very aggressive, they get hit on ever five minutes by a guy who they aren't interested in, it becomes nearly impossible to "make yourself available." Maybe they see a guy they'd like to meet, but if they appear open to conversation, five other guys will pretty much rush in right away. So they shut down and lose all interest in talking with people, or just stop going out to those bars altogether.
Nobody likes a bad ratio, but I've actually found that men and women are happiest closer to a 50-50 ratio.