Just watched this movie. It's stunning how much love and care was put into the practical effects and especially set design. There are white actors playing chinese princes, which is quite jarring (apparently their access to Chinese actors was very limited because the film was made in Spain and China was under Mao at the time). Still, it is definetly entertaining and worth a watch!
In my opinion, what restroom to use depends on what you have between your legs. "Gentlemen" for penis. "Ladies" for vagina.