I had that happen to me! After a few such experiences, I don't let it bother me in the states, although it's rarely an issue. Actually, this brings up an interesting etiquette question. At work, I'm often there in the evening when the cleaning people are working. I've had it happen where I'm sitting down in a stall going about my business, the cleaning lady comes into the men's room and starts cleaning, mopping, and so on, seemingly not caring that I'm there. So, adopting their lead with this "okay if men use men's restroom while female cleaner is present" mentality, on another day the cleaning lady is already in there when I enter. I proceed to use the urinal (not near where she was, and she didn't see anything other than my back), and she drops her sponge, yelps, and runs away. So if there's some sort of unwritten rule, it's inconsistent and/or I just don't understand it.