will be in Vegas next month and looking for some advice as to which hotel bar usually has a fair selection of hot women looking to provide some "companionship."  Any advice on when to go, which bars, and even any specific providers will be appreciated.

Why chance it with an unknown bargirl when there are so many reputable independents you can learn about from a board like this?
An unknown bargirl can pull off too many scams on an unsuspecting visitor, only to vanish into the night.  One of the well-reviewed independents would not try and pull something off that you'd be risking by inviting an unknown up to your room.
Or, if you prefer services, I'd suggest Pretty Maids, as they are well-reviewed and known to be honorable.

I agree with Jeffrey 100%.  No need to take the risk.  Plenty of Grade A ladies with lots of reviews --- And from what I have seen (and heard) no $$$ savings by working the bars.  IMHO