If you are coming in from the airport using Osceola Parkway, there's an easy one very close to Pop. At the intersection with International Drive - you can't miss it, the huge Gaylord Palms will be on your left - make a left onto International Drive. The Publix will be on the left before you get to Highway 192. To get to Pop after your stop, come back to the Gaylord Palms, make a left onto Osceola Parkway and then once you enter Disney Property, make the right on Victory Way (Wide World of Sports will be on your left). Pop Century will be on your right (you'll be able to see some of it from Osceola Parkway.
This is the Publix we always use at Disney World. Very easy to get to from property.