May I recommend the interested reader to watch La Haine[0] ("hatred") by Mathieu Kassovitz. This movie really sets the mood, and things barely changed since '95.
To be fair, such "ghetto" (la cité) people† mostly don't speak "verlan"[1] ("l'envers" with reversed phonetic syllables) anymore, but both the people and slang is usually referred to as "wesh"[2], from an arabic informal salute interjection. It's mainly poorly syntactically and grammatically worded French combined with limited vocabulary and heavy hand gestures and exaggerated arabic accent borrowings (e.g Rs are more pronounced) with various word borrowings from English or Arab.
Interestingly enough, I watched it recently in close proximity with The Wire[3], which provided great contrast yet striking similarities, and brings an interesting light into how we used to consider surveillance. In that regard, things have changed a lot. An awful lot, and certainly not for the better.
† It should be noted that many people and families that live there have adequate education levels and just live there because the rent is cheap and they can't afford anything else.
But after some reading, it seems you are right, as people in the ghettos still speak French, and not necessarily fresh immigrants.
http://en.wikipedia.org/wiki/Social_situation_in_the_French_...