My stay at POFQ overlapped Pop Warner for a day or two last December. I personally didn't see or hear any participants at the actual resort, though my mother said that food court was packed with them one morning. However, as I was trying to take the bus from DD to BWI for dinner, I encountered a very large group from NJ. By the time they all got on the bus, there was room for only about 6 or 7 other people. They then proceeded to cheer loudly (with their chaperones) for most of the bus ride, getting off at the Swan. Granted, the cheering was annoying, otherwise, they were nice and they did listen to the guidance of their chaperones. At one point it became clear that an elderly man in the back was livid with their cheers so their chaperones made them stop, which they did without complaint. I did later see this same group walking along the boardwalk at BWI cheering in unison. They were eating dinner at the ESPN Club.
As for the parks, I actually never seen them anywhere inside the parks. However, I think I stayed typically in the Epcot area during that time and I doubt they were much interested in the World Showcase.