I'm thinking of starting Jui Jutsu, I have a friend who's black belt and he recomends it. I want to do it more because I need the exercise than to defend my self. I come from quite a rough town thus I'm pretty handy when I need to be but my love of beer is starting to show so I need something to counter act it...
I'd definitely encourage you to train in BJJ, especially since 95% of fights end up on the ground. But I'd suggest that you also get some training in standing up as well. I like a lot of Bruce Lee's philosophy when it comes to fighting, such as taking parts from all different kinds of martial arts that would be effective and making up his own style, that's what JKD is all about. He obviously trained more in standing up, because he felt if you can end the fight standing up, all the better. Though he still trained in grappling cause even he knew about the importance of knowing how to do it, but his view on it was he didn't want to be wrestling around with someone on the cement.... 😆
Realistically, not many of us are as fast and accurate as he is to be able to end a fight standing up, so I'd say it's a little more important for 'the average person' to have a balance of both standing and grappling.
I saw a video of the Gracie brothers fighting against people who were in Karate. The Gracie's always shot in, grabbed them and took them down where the person in Karate had no experience. The fights never lasted much longer after that, and they won either by submission or tap out. On that same tape was a match between a well known Wrestling coach vs. one of the Gracie brothers, both obviously being grappling disciplines, but the wrestler didn't know how to get his opponent into a submission hold. It was a great match, but the Gracie soon worked his way into a submission hold and the wrestler had no choice but to tap out. Anther match was against a huge street fighter, and a Kickboxer, all with the same result, on the ground and into a submission hold. All that to say, learn as much BJJ as you can. 😉