If they offer them when do they usually make them available for reservations for May? If I book at the regular price then when are they offered for discount will they adjust the price?
Yes, see this historical info:
http://www.mousesavers.com/historical-information-on-walt-disney-world-resort-discounts/#2012
They will adjust it if there is a discounted room available for your resort for your dates. It's not automatic, you could call and they could say your room type is not available and you would have to decide if you want to switch your room or dates to get the discount.
The short answer is no. You have to rebook to get the rate. In most situations it seems like you are just getting a price discount, but that resort might not get an AP rate or that room type might not have the rate, so you will have to make a change. Just because you booked a full rate room does not mean you will be able to get the discount.
If they offer them when do they usually make them available for reservations for May? If I book at the regular price then when are they offered for discount will they adjust the price?