I can tell you that we have a very diverse program at Mount Sinai and are definitely not just a boys club. PM or post if you have any specific questions.

I'm a female and rotated at both NYU and GWU this past fall. GWU has a very high percentage of females and NYU had five (I think, also don't know about their intern class.) I did not feel weird at all at either place. I come from down south where I did have the pleasure of working with a resident that believed females didn't belong in ortho and I didn't get that feeling from anyone up north.

Wake Forest has traditionally been a "female friendly" program. Currently there are five: one chief, two PGY 4's, one PGY 3, one PGY-2 (out of 3 or 4 in each class). The whole gender thing isn't even an issue. There are usually 2 or 3 general surgery interns as well. The girls in the surgery programs (Gen Surg, Ortho, ENT, Plastics) get together once every couple of months for dinner/drinks. It's nice to have a group of women to talk with about career decisions, workplace issues, and stuff outside of work. I would also recommend talking with any female faculty you may have in your institution (ortho, general surgery, etc) and ask for their experiences.