there is a winn dixie not far from the main strip of hotels (we stayed at saratoga one year and went to winn dixie) they offer a store card that is easy to sign up for . Just go to customer service ask for the card (don't even have to register it) and use it to get some good deals. they also offer gas points on the card as well (nice feature for the refill for the rental).
Winn-Dixie
7840 West Irlo Bronson Memorial Highway, Kissimmee, FL 3.5 mi SW
there is also a publix (they tend to be alittle more expensive).
Have fun!