Reminds me in Louisiana they(the government) they forced people to speak English. The children could not even speak French on the playgrounds with each other or they would get in trouble. Them trying to get them to speak English happened after Louisiana became a state. Some parents refused to send their children to school because of this, but they forced them to, so they choose to bring their children to a private french school(which ironically taught French and not cajun french). Then they forced all schools to teach in English instead of French, and parents pretty much were pretty hesitant to teach their kids French because it got them in trouble.
Moral of this history lesson? While what you are doing is trying to make sure everyone is able to communicate each other, it can kill a language and kill part of their culture. Very few people now can speak Cajun French. Soon those who can will die and it will just be a thing of the past. Don't impose people to change their language, don't punish them to use it. Most people speak German in Germany, most of the signs/writing is in German, what are you worried about? People will assimilate to understand it, but don't change their culture/heritage. Chill out.