(Repeating an earlier answer:) For some mysterious reason Google has not made the language preference a central account property. When a language preference has not been set for Google Docs (or Drive or Sites) then the system tries to guess it based on IP address or something else, and the guess may be wrong. In that case the user needs to set his or her language preference, and it needs to be done for Google Documents (Google Drive, Google Sites) even if it has already been done for other Google products.
The language setting is found in Document Settings under the little wheel top right on the docs.google.com (drive.google.com) home page. Of course, everything will be in the foreign language, so instead one may go directly to this page.
If that page comes up in English then fine; otherwise, expect that the language setting is in the topmost menu item. (Below it is the timezone setting, and there are a few other things.) Make your language choice, and then Save it; this is the middle of three buttons at the bottom. (To the left of it is "Back to Google Docs" and to the right of it is "Cancel"; avoid those.) The Save step is critical.