can't help you with pin code info, but for general public discounts, seems like they usually start around January 3 or Jan 4 (so after the "holiday" travel is pretty much done.) So those wouldn't help you any, because even though the discount starts in the middle of your trip, you can't apply the discount when you check in before it starts. The only way you'd be able to take advantage of those kinds of discounts would be to have a split reservation...your first few days on one reservation and then start a new reservation on the day the discount starts. Which might not work very well because if you're doing a package, you'd have to have 2 separate packages...very expensive way to do tickets.
here's a link to mousesavers page which lists all the "historical" info so you can see what kinds of offers happened in the past, what dates they covered & when you could book (note a lot of the January offers did not come out until late October or early November.)
http://www.mousesavers.com/historicalwdwdiscounts.html