Around boyfriend, its "potty" or "tinkle" or "pee"
If I'm feeling silly, its "use the little _________ 's (fill in whatever I'm engrossed in at the moment) room. For example, if I'm programming "I've got to use the little programmer's room" If I'm drinking, its "I've got to use the little drunk's room"
For polite conversation, I will excuse myself to the ladies room.
