Blue Dragon leaves some of the music intact, but not much. Generally it's anywhere from one piece to four pieces per episodes. Infact, I've actually seen ViZ swap another Japanese track for another (which happened in MAR quite frequently) a couple times so far.
However, what bothers me more often than not is the fact most of the music changes generally are removing Nobuo Uematsu's score and leaving Megumi Oohashi's intact the most. Nobuo's music is in the dub, but it's not heard as frequently at Megumi's.
Actually, this bugs me. If anything, Nobuo's score should've been one of the selling points to the show. "Music by the composer of the Final Fantasy series" could've been used effectively. But... Apparently not.
The intro and outro songs being removed weren't a total surprise. ViZ has done it in early Naruto, for instance. As well as a nuraber of other dubs. However, it's not like a kid is going to suddenly stop watching because they hear songs in Japanese. Infact, I'll never understand why they just don't leave the song alone or just dub it and be over with it. But I suppose the songs generally aren't a big part of the show, while the BGM is...
I have more issues with the dub for Blue Dragon, but I realize this topic is about the music for the show, so I'll leave it at that. In any case, there's been "some" confirmination that ViZ Media is working on an uncut dub for Blue Dragon. I guess all we can do is wait for that. If it ever comes, that is...
Hopefully if (or when) they release it here in the United States, ViZ doesn't decide to keep the op/ed songs replaced, like they did with The Prince of Tennis and Mar. Not to mention, leaving it uncropped. Since the UK release is apparently going to be Uncut, I guess we'll find out then...