Many times when I try to tell housekeeping "No Service Today", they either come back with someone that understands English or I get a call from their supervisor asking what I had told them.

I've been to some properties that give you several choices of door hangers, from Resting Come Back Later, No Service Today, to Ready to be Cleaned. Only presuming the staff understood what they meant.

If I'm doing a late check-out, I will take some note paper and write on it: Checking Out at 3:00 pm with my room number and put it in the key slot outside the door. At least that they can take to someone to translate if they need to.