You can get a discount as long as there are any discounted rooms available.
Just call the regular WDW # and try for a discount. Tell the CM your needs. First they will try to get the discount and apply it. Then they will connect you with special needs dept. to help with accomodations.
At the Polynesian, most of the accessible rooms are in one building, Rapa Nui. It is close to the TTC, the rooms are large, and there is a parking lot directly in front of the building.
At the GF, the rooms are scattered. We have also had an accessible room at BC but only once and I don't know where others are located.