There are currently two English versions of the film. Both can be found on the Australian DVD released by Madman in June 2006, one as the subtitles and one as the English language track.
The dubbed version was actually released on video in the US in 1995 by Best Film and Video and features dubious voice-acting and an appalling collection of errors big and small.
The subtitles, while unexceptional, are by comparison quite faithful to the original. There is only one serious mistranslation. It concerns the vegetables which Godo brings to Earth near the end of the film: in the subtitles he insists that everybody in the world can eat them to revive the Earth, while in fact he plans to cultivate them - a rather more practical way to repair the environment.
On the whole I recommend the subtitled version. But if for some reason you only have the dub, this synopsis might help you understand what is really going on.
The synopsis is divided into tree parts. It can also be downloaded as a single RTF file, compressed with pkzip.