I'm south of Atlanta too in Henry County & rode at Dauset Trails earlier today. I found that there were enough yellow fallen leaves on the ground to create a sort of floor between me & the remaining mud. With how dry it's been these last few months, I don't think we're going to be able to get enough rain before winter to really do damage to the trails. If the mud on your tires becomes flush with the knobs for an extended period of time, it's probably too wet. At Dauset or the Horse Park, I generally don't worry about it. They're trails with obstacles that are built purely by erosion anyway, so it's not really a big deal. When you get to trails like Blanket's Creek with man-made obstacles & such that have to stay a certain way to remain fun & functional (like berms, seesaws, jumps, etc) it's best to stay away when they're more muddy than not.