Well, I play guitar, bass, trumpet, piano (poorly), mallet percussion, drum kit (poorly), and some other assorted percussion instruments. I'm pretty good at picking up things to the point where I can play simple songs, but the only instrument I consider myself really good at is bass.
I wish I had more inclination to practice playing piano; I'm not very good at it. It's hard to go wrong with jazz, even the stuff that's really "out there".
Horn... you mean brass? (some people I know call everything a horn, from a clarinet to a tuba, so I have to check) Trumpet's fun, if a little difficult to just pick up and play. I've never played a french horn, so I can't say much about that, but they do sound nice. The lower brass instruments tend to be easier to play (except maybe the tuba, that takes some serious air), but I never put much time into learning how to play them, so I can't say much there either.
That's terrible! No one should be banned from taking a class, especially something like music.