We were there September 15-22 and we saw them most often at our hotel, All Star Movies. I didn't see many in the parks, but when we waited for the bus at our hotel, they were present. I wouldn't say it was a swarm, but it was a bit annoying.
A little girl who stood in line with us just FREAKED OUT when they flew into her or near her face. Her mom put her in her little sister's stroller and covered it up with the thin blanket. The little sister, about eighteen months old, didn't seem to mind the bugs at all.