Hi, I'm the guy who's been translating DQM 1+2 (along with Devil Children and Oriental Blue, which already have been translated but aren't ready for a release yet).
I couldn't give you a good percentage of how much text has been done in DQM, but a decent amount of the text has been translated in part 1, and only a small bit of part 2, but most importantly, almost all of the boring menu stuff has been done for both of the games. That's the hardest part of the translation! (Dealing with all of that tedious stuff!) The battle text has also been translated, but it's FULL of errors because the Japanese sentences are broken into fragments at times. The menu and story files that I've translated add up altogether to 444 k of text, but this is only a drop in the bucket. I'm guessing that it may be 1.5 to 2 megs altogether, but that's only a hunch. If you conservatively round up and say it might be a 2.5 meg script (Wow.), then that would mean the translation is a little over 20% completed, and that's probably a fair guess.
But in any case, I will be moving in less than a week, and it'll be a while before I can get back into the swing of things, so it may be a couple of months before you start seeing any more progress on DQM. In the meantime, I'm hoping that Kingcom and Kaioshin can crack down on Oriental Blue and Ice Book!