We stayed at AoA last year and walked across the bridge to Pop quite a lot, either to check out the resort, use their food court, shop in the gift store or use the buses. They are not 'sister resorts' so you can not use their pools. We did, coming from the parks, jump on quite a few Pop buses if there was no bus or a longer line for AoA and it was a very short straight walk from the food court across the bridge back to AoA. It was really nice to be able to take advantage of two buses, two food courts (which are completely different from another) two gift stores etc.