It is quite unusual to see MENS or WOMENS on 'public' toilets -sometime in pubs etc they may do this to generate some interest in the mistake. (trying to be funny!) but usually the 's' is dropped. Then again in the same breath I wonder about GENTS which has been totally accepted as a correct sign but basically is an abbreviation so should have an apostrophe. So strictly it should say Gentlemen's toilet , the 's' indicatiing that it belongs to the Gentlemen , (which of course it doesn't as it is a 'public' toilet.)
If it helps the Spanish signs for 'Gents' were totally
confusing at first but we learn from our mistakes!
I tried to help but found that the more I it tried the less I could could give ther right reason, but MENS and WOMENS are not correct! Adios!
correct