My dad bought me my first couple of jocks. He saw me in mine and I him in his too many times to count. He was a single father raising just me there wasn't a lot of need to be modest in my home growing up.
Why cat there be a jock convention? Seattle allows for public nudity as do any other cities that participate in the naked bike ride. If it's held at a private convention center there should not really be any issues having one what do ever. And I for one know I would definitely be in attendance.