I see housekeeping work 4 rooms at a time, staying in one area for 10-20 minutes. I would not want to keep a client waiting, it could also really screw up your day.  
Just walk rite in like your supposed to be there. Leave the door propped or be ready to open it so there is no awkward time standing in the hall.
The manager at the hotel a couple other ladies and I use often commented how amusing it is seeing guys walking in shuffling through papers, hiding in a newspaper, carrying a empty bag etc. trying to look like they belong and standing out like a sore thumb.  
Especially in busy hotels the staff doesn't care or even really know who's supposed to be there. No reason to delay peoples days.

Ive only had one person ever care that housekeeping was next to my room. He turned around and went to the bathroom then lingered waiting fir them to leave. He wouldn't come even after I told him it was ok. After a few min I spelled out he had nothing to worry about and he came in. That drew a heck of a lot more attention then someone walking into a room.