Yes, I think the whole series has been officially released by Viz. But, just as many of their other mangas, they butcher it. The early volumes (1-4 maybe?) were pretty good. But when they rereleased those volumes, they cencored everything, to aim toward an audience of 5-year-olds like the US tv show. The quality of their editing isn't that great. And for whatever reason, they started using english names for some characters. I don't really mind that with some (Pegasus J. Crawford to Maximillion Pegasus), but every now and then they switch between the english and japanese name. It just confuses people who haven't read it.
Most fans of the series are generally disappointed with the official english version.
There are other reasons, (mostly involving the quality of Viz's work) but I won't go into them.