Yes there is a discount.
During Value Season you can get up to 15% off at the Disney Deluxe and Home-Away-From-Home resorts, or 20% off at the Value and Moderate resorts and the Ft. Wilderness campsites.
During Regular Season you can usually get up to 10% off at the Disney Deluxe and Home-Away-From-Home resorts, or 15% off at the Value and Moderate resorts and the Ft. Wilderness campsites.
During Peak Season you can usually get up to 10% off at the Disney Deluxe and Home-Away-From-Home resorts, or 15% off at the Value and Moderate resorts.
The only time
AAA/CAA discounts don't usually apply is Holiday Season (around Christmas).
This was taken from Mousesavers.
Hope this helps!