OP, October is a crazy weather month. It generally starts off unbearably hot and then, at some point, the humidity breaks and it is wonderful. But it can also get cold, especially mid, late October. So if you don't want cold AT ALL, you should probably avoid October.
We can't predict weather, of course. We also can't predict crowds...but October is no longer the low-crowd month it once was. It's almost impossible to find a low-crowd time these days. Check the touringplans site for good guesses on crowds.
Good luck!!