Sentence:  Downstairs, he was informed. That is, down the escalators, where there is both a women's room (often with a line) and a men's room (almost never with a line). Or <WSD>alternately</WSD>, he could ask the station master to buzz him into the “family” bathroom. He opted to go downstairs. 
Meaning of the word marked with <WSD> tags:  Alternatively.