Jesus OP, this isn't some sort of fraternity/college party. This is a chance to meet your potential new peers. If you hook up with the wrong person or if it doesn't go right, then you have to spend the next 4 years with this person and his friends, in the same exact classes, and potentially in the same lab groups... And believe me when I say that med students gossip. It's what we like to do and your class size isn't big. So you will have THAT label of hooking up with a guy during interview day. Something you don't want.
Case in point: some guy came to med school and for the first two months, he would leave every weekend to go to some frat party back at his college. Every friday he'd bring home a different girl back to his place before deciding that he was over that lifestyle (and he was bombing his classes.) Well, now he has the label of "that guy who sleeps around a lot" and no med school girl will touch him. Sad too, because he's actually a really cool guy. And a girl had a crush on him before she found out about what he did, so she lost interest.