Hotel guests change pretty much daily, in the larger hotels it would be literally impossible for the desk to keep track of who is or isn't registered at any given time.  Then take legitimate visitors to registered guests into account and it gets worse.  There are hotels that require a room key to access the elevator, but I stongly suspect that a lady with any sense won't be there...
The few hotel incalls I have been to were motels where each room had its own exterior entrance. So the above is (again) mostly conjecture.
I think more about the less urban areas with a limited number of hotels.  Do the desk clerks notice the same ladies coming to visit time after time?

Get a small backpack and carry it on your back with you. When you walk in the hotel walk to the elevator and get to room without looking around alot. You want to act like you are staying at the hotel. Now if the hotel is the only around in one of those small country towns watchout. If you enter in the hotel after 11:00 pm you might have to ask to get into the lobby of the hotel.

I always wait in the lobby until she calls and no one has stopped me yet; those are large hotels. One time, a lady had to postpone the meeting because she had to change hotel -- it was screening evening visitors. We would hope that the ladies would pick the right hotels.