Many bio-guys in my class cross their legs. Then again, my class pretty much consists of nerds and eccentric intellectuals. We have two male Twilight fans, several guys who watched The Powerpuff girls when they were kids, and no "macho men".
The "manly macho man" guys in my previous school sat with their legs in the ankle-to-knee way. The kind of guys who were very vocal against "->-bleeped-<-s, ->-bleeped-<-s, the immigrants, etc".
I sit with my legs crossed sometimes, and then the ankle-to-knee position if I'm sitting on, say, a park bench and reading. It provides a nice sort of "shelf" for the book to lie upon. I don't pack, so I s'ppose it looks a bit odd, but who cares?