I dont remember hotel 81 must pay deposit.... is this a new rule got $20 deposit?
Just go to the recep say you want a room for 2 hrs (min 2 hrs) and pay the $20. They may ask you whether you want to join as member for $10. Personally i feel no need as it doesnt give you much benefit.
Enjoy bro and dont forget to tell your gf to scream and shout louder the better. Else she may by habit keep low volume....
And do post a FR here after your trip to share your first time experience