I dont think its faux pas to negotiate a date set up, unless a lady specifically says it on her ads or website. like dentonseek mentioned the way you go about it or the approach you make is very important. if she says no, then respect that, apologize if she felt offended and move on. dont haggle.
I would suggest you make the date a very nice one. I am not talking about a matinee movie, dinner at sizzlers, and a two hour romp in the sack when you wanting to pay the rate of an hour.
make it worth her wild. or dont ask in the first place.
one of the reason I like to go to Austin to hobby, is because I know several ladies that always are up to go get drinks, dinner, head out to sixth street after or before BCD. I dont want to be with a clock watcher as much as she doesnt want to be with me. Its a different mentality down there and I have become good hobby friends with them and I refer other clients I trust to see them, because I know they will take good care of them too.