Yes, feel free to ask. Obviously, it's all about trust and chemistry. If they say no, don't take it personally! If you still want to visit them, this shouldn't be the show-stopper. It's common sense for many ladies, especially the younger ones, who think of this job as a temp solution to their financial issues, therefore, they try to keep the business relationships separate from their personal which is fully understandable.
FYI, although single by all means, I do have a cell number only for this side of my life. And, it normally goes on after 10 PM when I hit the road!