Why wont it? When you first join there is only 1 forum which is a url forum (not a real forum).
It has a link that goes to:
http://www.website.com/profile.php?do=editusergroups
Which lists all your languages:
English (*)
Spanish ( )
Italian ( )
They click their language and press "join".
And it's done.
All you need to do is create 1 URL link forum and 3 public joinable usergroups.