I don't think this is possible, although there are players that don't speak french, you can't force the french players to speak english because they outnumber all the other nations in this game and some of them simply don't speak english.
no.1: french players don't read the english forum, so it's kinda useless to write here
no.2: this game has it's origin in france
no.3: most (and the top) players are french, so it's normal that most of the messages will be in french.
no.4: in an international game everybody tries to comunicate as best as possible, more known languages the better, but you can't enforce a language to be used.
no.5: this topic doesn't really belong here so I guess I'll close it now.
good luck to everybody in comunicating with our french friends
(lucky me I speak some french... )