^Tarantino always cameos in his movies. There would have been something lacking had he not. Also, I think there's meant to be humor in that scene. We're supposed to recognize him, and realize he's doing a ridiculous accent. Someone that doesn't know Tarantino wouldn't think twice about it, but a fan would recognize it and laugh.
I was thinking about that scene a little and maybe it's overplayed to show that Django sees these guys in a different light than at the beginning of the picture. Now that he's been free he sees these guys for the clowns they are. (Maybe? Just a thought anyway...)