I like watching MMA, and I took a Brazilian Jiu-jitsu class last year. Before that I had trained in karate, akido, kung-fu, tae kwon do, along with some self-taught nunchaku, bokuto, tonfa, and staff work.
BJJ is a good form, but it's kind of like the next karate. You can find places training brazilian jiu-jistsu all over the place thanks to the UFC (Gracies), so try to watch out for second-class instructors. Not only is training under a wannabe a good waste of money, but I've seen people injured because their "master" didnt know what he was doing.
Personally I'm not as in to grappling. I like to strike. In a real-life situation, submissions are more practical against a single opponent (eg. you wont get sued for knocking out an assailants teeth if you get them to tap instead of KO), but training an art that focuses more on striking might be better for your injuries. Kata are a great way to stay in shape and mentally relax, and probably wouldnt strain you as much as grappling.