I know this post says "for girls only", but quite a few men have responded already, so I'll add my 2 cents' worth.
A number of summers ago, I was traveling and camping in the eastern provinces of Canada and discovered something regarding the use of bathrooms at campsites that differed in the English provinces of New Brunswick, Nova Scotia and then in the French Quebec province.
I camped for a few days at the Forillon National Park in the Gaspe'. It is one of the most beautiful sites for a park/campground I have ever stayed at. It sits atop towering cliffs that descend straight down into the Atlantic Ocean. (But I digress, lol).
The first morning I was there I went into the men's bathroom to shower. I was in a shower stall with the door closed and soon I heard what sounded like two female voices. I turned the water off for a few seconds to be able to hear better, and sure enough, two women conversing in French. (I had know idea what they were saying). A bit of panic set in when I thought that I had gone into the women's bathroom by mistake.
I continued to shower as I heard them washing up in the sinks and brushing their teeth. I waited till I heard them leave to come out of the shower stall and immediately looked around and spotted some urinals on a far wall. Relief set in. As I exited the bathroom, I looked at the sign on the outside of the door just to make sure, and, yep, it had the international symbol for men!! When i told my girlfriend what had happened, she said she heard men's voices in the women's bathroom when she was using the toilet.
Later that day as we got friendly with some of the other campers, we asked about it and were told that in the French-speaking provincial parks it's common practice to treat all the bathrooms as unisex..If one is full, just use the other.