To make a long thread short, most strip hotels require some sort of conformation people getting on room elevartors are registered guests. Usually this takes the form of showing their room key/card.
This is particularly true after 6:00 PM. So meeting your date in the lobby or bar and escorting her to your room is the normal way of handling the situation.
The only hotel Im aware of that is apoplectic on the issue is Harrahs. The ones you mentioned do have security but will not caue you a problem if you follow the procedure outlined above.
Now go have fun lol!

I have stayed at the Venetian with no problems.  Also at the Monte Carlo which did not require the romm key ID thing last time I was there, could have changed.  Follow the rules stated above and confirm everything with the lady you a planning on visiting with.

There's three options:

1) show a room key

2) have security call up to the room and ask if it's OK for so and so to come up

3) meet them in public and escort them up (flashing your room key)

Nothing really awful, unless the provider is banned from the property and risking a trespass arrest, none of these options is a concern.  The only concern is if you happen to be famous and you got paparazzi after you.

Bob