My friend has really poor social skills.?

We've been really good friends since freshmen year. Coming into highschool we were both socially awkward and that's pretty much why we became friends. Four years later we're still great friends, but the difference is my social skills improved while his didn't really change that much. He did become less shy which is a start. But when in a real social situation he doesn't have good judgement. A few examples. Whenever he talks to people he rambles on and on about one subject only and he's never open to change the topic. Another time he going on about how healthy he is because he never eats junk food, while we were at a party. One more is he is obnoxiously loud and annoying, and makes jokes that sound like they would come from a mentally retarded person. I don't know if his ADD contributes to any of the above, but I'm nervous for him because he's starting college along with me and I just don't know how he'll do.