I second the emailing them early. I emailed one girl a month and a half before my scheduled interview and it took her 2-3 weeks to respond... she said no. I emailed another girl and it took her 2 weeks to respond... she said yes, but she wasn't going to be back to her apartment until around midnight (which was a little late for me). By that point, it was too late to ask anyone else, so i booked a hotel. However, I ended up getting into a school I'd rather go to a few days before the interview, so I just ended up cancelling!
I chose the two girls because they were both from NJ (like me).
So, yeah... do it early and try a few people at once instead of waiting for one to respond before you contact another (like I did).
Good luck!