The best way to do this is find some way of remembering what language to use, then set a constant with that language code very early on. Here you would take the last URI string (using array_pop() in a pre controller hook perhaps?) and set define(‘LANG_CODE’, ‘en’) or whatever fr all of CI to see.
You cannot actually translate page content without hooking into google Translate or some other third-party lib, but you can easily have language specific content. By storing a language code in the database next to the content, you can say “SELECT * FROM news WHERE lang = ‘en’ or lang = ‘’” and you have your site accepting multi-lang.
If you need a little help with this here is a post with a few examples on how to do this.
How to make a multi country web site? (Best practices)