To give a little bit more detail to Edd's directions:
Use the airport's NORTH exit
Proceed west on the Beachline Expressway (TOLL 528)
At exit#3 proceed north on John Young Parkway (CR 423)
The Wal-Mart super center will be on your right about 2 miles.
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For the store that's closest to Disney:
Use the airport's SOUTH exit
Proceed south on the Greeneway (TOLL 417)
At exit #6 get off onto SR 536
At second traffic light, turn left onto SR 535 and the Wal-Mart
super center will be on your right in about 1 mile.
BobK/Orlando