Basically, here's the deal, ladies are more than welcome to show up, but a few basic pointers:
1.) Don't manhandle every gay guy because we're safe, you're drunk, you're feeling bored/insecure/horny or any other reason. It's a gay bar, most guys are there to be guys and not deal with awkward clingy physical girl moments, this is doubly true with thinking you can just randomly grope a gay stranger. Yes, many of them don't care/won't be bothered but many will. Further, just because you are in a gay bar doesn't mean there aren't straight men. Or predators. Being in a gay bar probably makes you a bit more safe but it doesn't make you invulnerable.
2.) Pick an appropriate scene. Do you want the stereotypical guys with no shirts and ripped abs dancing to horrible disco house music with glitter on? Go to the trendy/twink/hip/fashionista bar that caters to it. Want to relax with a beer after work in a low key no pressure scenario? Hit up the gay dive bar. There's no reason a woman can't show up to, for example, a bear bar, but I think I would caution women to generally steer clear of most serious leather bars and bars notorious for having hook up activity on the premises. This isn't because women can't handle these scenarios, but more because it is far more likely you will be out of place and make gay guys trying to enjoy a dirty night in drunken semi-privacy a little weirded out. Remember, the gay bar is often a refuge for guys who don't have a lot of places to meet other available guys and escape from judgmental environments. I live in a city with a huge gay population, but we still have far less "bump into a stranger get asked out on a date" moments at coffee shops, libararies, work, whatever than you do, so respect that the bar is kind of a big deal for a lot of people, and we've got no problem with you tagging a long.
3.) Don't make us habitually babysit you everytime we go out because you got too hammered to function. See #2 for "this is kind of a big deal" for why.