I'll be in Vegas in about a month on biz. First time in 20 yrs. Was going to schedule a girl but I have no idea what my schedule will be. Last time in town I was hit on by a few attractive  ladies in the hotel bar. I assume that still goes on. Is that not a good option?

This is a well regarded agency. Get pre approved so that you're ready to rock and roll on short notice.  

No,that would not be a good option especially since you know about this site.
Why go with an unknown lady when you have all the required tools to make an informed decision?
Why not reach out to some providers who pique your interest explain your situation.
Let them know you would like to be screened that way when you are in town and have some available time you will not have to wait for screening.
Ask the provider or providers you are interested in if this is something that they would be willing to do.
Good luck to you!

Better to get acquainted and pre-checked with a couple of girls, explain your situation and give us your possible window of opportunity so that we can keep ourselves semi-available...

while i can not meet short / last min, with 24 hours notice i can put you on my schedule

There was a horror story about one casino gal only doing oral and never disrobing so he didn't know if she was a man or woman. Another horror story about a guy passing out to discover she scanned his credit cards with a portable scanner that attaches to her smart phone.