I'm not feeling the risk--I didn't need to know Japanese to play through Diamond and Pearl aside from a single part where a Team Galactic member runs two screens out of town and I didn't think I was supposed to chase him, and that was a totally original game.
As long as I talked to everybody in every town as I reached them and also as I re-reached them (e.g. when there was a shortcut to a certain town I'd already visited now that I had Cut/Surf/whatever, I figured there may be something new there), it turned out fine enough. And for that one Team Galactic incident, I'm pretty sure Serebii people were already past it when I got there even though I was only a couple days behind (by virtue of shipping time).
As long as I talked to everybody in every town as I reached them and also as I re-reached them (e.g. when there was a shortcut to a certain town I'd already visited now that I had Cut/Surf/whatever, I figured there may be something new there), it turned out fine enough. And for that one Team Galactic incident, I'm pretty sure Serebii people were already past it when I got there even though I was only a couple days behind (by virtue of shipping time).