I don't know if there was much of a presence at DragonCon (as there was no discussion on a group meetup and anyone I know from the RPF I just ran into as I was walking around), but there were a few RPFers there that I know about from the post I made a while back.
Honestly, I'm surprised the RPF doesn't have a booth set up at conventions every once in a while. In fact, when I took a picture of this girl who had a pretty accurate Chell costume from Portal 2 with an amazing replica of Wheatley, she asked if there was a booth for the RPF at DragonCon when I told her about the RPF and how to visit the forums.