I use the Wal-mart store out on Hwy 535. Go out past Disney Springs, turn right, go under I4, and it's a few miles straight down. Lots of ways to get there (out the road that runs in front of Epcot is the best) but you get the general idea. It's on the NW corner of where 535 crosses Osceola Parkway. There is a Publix across the street from Wal-Mart there (NE corner) and a Wawa that sits up in front of Wal-Mart facing 535. Look on the lower right of this map I grabbed for the "WM", "Pub", and "WW".
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You can go almost any direction from WDW and run into a Publix or a Wal-mart.
Bama Ed