They get along, you're right. Ellie just seems to find Julian an annoyance and Miguel acts surprisingly antagonistic towards him whereas Jerry is amused by their verbal sparring. I think my favourite J/J scene is when they discuss their nicknames at school. Mad Dog and Diablo, the dynamic duo. :D

I've said before, I think Julian intends himself to be the annoying one. And deliberately being a pain in the ass, he's still more likable to me than Miguel.

I love that theory, btw. :) Julian works at being repulsive (and fails), but Miguel does it naturally.