Anyone that bought the Russian version of BF3 you need to download the English files to get the game back to English.
Download here as a torrent
Or direct download from here, I uploaded this myself so it is legit.
You need to put the files in the loc folder in C:\program files x86\origin games\battlefield 3\update\data\patch\win32\loc
and then delete the Russian files. If you get a black screen you also need to delete the Russian files in C:\program files x86\origin games\battlefield 3\data\win32\loc