On several occassions I've tried to get that little bit of extra sleep, only to have the maid come knocking on the door. Knowing how to say come back later (or not at all) would be useful.
It would also be nice to know how to talk about some of the more typical things like I need towels, change the sheets (or not), I need an iron/ironing board, more soap, toilet paper, or even I don't want service today, I just want to sleep!
I think it would be good to be able to talk about how much longer you're going to be staying in the hotel, as I had a maid ask me this once, and I fumbled my way through it.