You seem to assume here that only users who don't speak English like i18n'ed software. That's untrue. I do use a fully localized system and I tend to think that I speak a quite decent English.
Mmm, same here. Still, I don't like it half-and-half - having to produce English text (the bug report) in a localized environment would seem a bit strange to me. If a localized agent were to guide me through the reporting process I'd automatically "respond" in the same language. C.