Can you put on some pants before you talk to me?

About a month ago, I joined the gym (excuse me, "fitness center") at the college where I work. It's a pretty good deal - $300 a year, taken out of my paycheck. Sure, I could use my landlord's very-old treadmill or walk laps around the resevoir, but the gym has some advantages - better and more varied equiptment, TV's, air conditioning, cute college girls (who I would probably be fired for talking to).

I've never been a gym person, or really exersized at all. So one thing I haven't gotten used to is the whole locker room thing. I still find it odd to have conversations with completely naked guys. Specifically, one of the professors I've had as an undergrad will frequently be finishing his workout when I'm getting in. So he usually says hi to me and starts up a conversation with me - while he's completely naked. Which begs the question - is it ruder to not look at him while he's talking (my prefered choice) or to look at him?