You should be OK for planting in North GA now. I don't grow turnip greens although I like them a lot. For our fall garden greens we are planting spinach, kale, broccoli raab, and swiss chard. Although I know I am planting too much already, I'm going to add some mustard greens since I like them a lot too :~).

The link is for a UGA Extension Department publication which I have found very useful. Hope it helps you also.

Here is a link that might be useful: Vegetable Garden Calendar