There's no way to determine percentage of gay/bi/straight breakdown at these clubs. As Shadowcat says above, even the "straight" guys are not narrow. Further, percentage of the entertainers willing to meet privately is impossible to determine.
Copied from a post I made a few days ago in the Reno Gold thread:
I think the best advice is to directly go to the club/event in person, chat your intended up in a very respectful/non-creepy/polite way, do a couple lapdances (be polite!), and then simply ask if he is comfortable with safe private meets with clients (do not mention words like "escort", etc.).....
Always be friendly, smile, have fun, listen, respect boundaries, and be polite