Oh god…the bane of trans* existance! The problem here is that neither of these restrooms are designed for my identity, and both have restrictions against my presence in them. Either one is dangerous to use. Try to go at home. 🙂
Before I was “passing” :p I would seek out family restrooms, and still use them sometimes for additional privacy. But even if you don’t pass you should just casually use whatever bathroom feels right.
If you’re genderqueer that’s maybe harder, but I know butch lesbians who regularly have this problem, and they solve it easily by replying to the stupid questioning by just saying: “I AM FEMALE.”