I remember a lot of articles in Outdoor Life, ( boy that makes me sound old!) With Lamar Underwood talking about hunting quail in that area, and in Delaware. Lots of birds, equal to anywhere. Seems like bobwhites thrive when New Jersey was predominately small truck farms, and the sharecropping the southlands, a time past.
I think it is possible to get them back. A lot of effort and research is being done and I think it will eventually pay off. A month or two ago I read an article in pointing dog journal or something about eye parasites in quail and they might have something to due with the decline in quail. I'll have to see if I can find it somewhere.