What do guys think of girls who don't dress up at frat parties?

Does it really matter? I like getting ready and going out with my girl friends and hanging out with my guy friends at college frat parties, but do they care if I don't go all out? I usually dress up but sometimes I'm just too lazy/don't feel up to worrying about heels and dresses. What do they think of girls who just wear jeans and a flannel or something like that?