EU - while exceptions exist, my experience generally has been that devs working in English are virtually always much better devs than their peers working in the native language of the land. Likewise, most business projects I've worked on were entirely English on the inside, even when the UI was e.g. german-only. I've also seen a few projects where the business domain is so thoroughly native-tongue (typically when the business domain is a projection of the local bureaucracy) that you couldn't name business entities in English if you tried. Those can end up with a somewhat weird hodgepodge, where the code and comments and such are still English, just the names of the entities aren't.