It probably wouldn't have been an option for me, if I hadn't gone to disablility services, shown them my AS diagnosis papers (as well as my hs IEP), and asked for it.
For coed buildings, there's a girls' bathroom and a boys bathroom on each floor (if it's a community bathroom building). Usually girls are on one wing and guys are on another. In the building I'm going to be living in, I will be sharing a bathroom with the girl next door.