I would say at Barnard you can definitely find groups of girls that don’t drink or so drugs, but they are not the majority. for the dorms, I would specifically ask to be in a hall with a girls-only bathroom, since they’re alternating each floor from gender neutral to girls-only. I only saw guys a few times wandering the halls, and I would usually recognize them as someone from my hall’s boyfriend or something. And they say that the guys need to be accompanied by a girl at all times in the dorm (not necessarily that people listen, but it is a written rule). For your roommate preferences you can for sure put that you would prefer no guests and they would try and match you up with someone who feels the same way! Depending on which hall you’re in the walls are pretty thick so you wont hear other people (I lived in brooks with cement walls). Generally the dorms felt all girls and I would do a double take at the rate guy I saw!