Walmart is huge! Like Publix there are Walmarts dotted all across Orlando. They are extremely large stores and they sell a wide range of food, drink, clothes, fabric, electrical goods etc. In fact there is probably not much they don't sell. You can buy Disney merchandise for a decent price at Walmarts too.
Although we shop at Walmart quite frequently it is really because we need to buy household items for the villa or because I like sewing and their fabrics are really cheap. In terms of food, it has a very wide range and the quality is like Asda (same company). From a personal point of view I never find the staff very friendly, the queues are long and if you ever have to take anything back to Customer Service be prepared for a long wait. We often buy our beer and wine at Walmart.
We usually use the Walmart at Haines City; Walmart Supercenter, 36205 US-27, Haines City, FL 33844, USA as per the google map attached to this and also the distance above.
There are however many more and one I will want to try next time we are at the villa is the following one at North Ridge Trail.
Walmart, 5100 North Ridge Trail, Davenport, FL 33897, USA = 10.2 miles :- 18 minutes
Walmart Supercenter, 4444 W Vine St, Kissimmee, FL 34746, USA = 12.7 miles :- 20 minutes