early registration sets aside a number of bibs for DVC/AP, but the remainder of the slots will be opened on general registration day. When early registration sells out, it doesn't mean the entire race is sold out.
That said, it's likely that the popular choices (Dopey, Half, 10K) will sell very, very quickly (1-2 hours or less from Noon, eastern time). Surprisingly, Goofy didn't sell as quickly last year. Not sure what it'll look like this year.
Log on early, refresh until you see the link to register, and have your CC/proof of time (if needed) ready to go. Good luck!