Help me, I'm confused.
You have four weeks remaining to be held in Juvie? Or four weeks before you go?
There is no "Arizona" detention center for juveniles, it's a county thing. Do you have any solid reason to think you will be assigned to the same facility his friend is in? And then the same unit?
If it's as tough as you say, I'd be worried somebody will kill your brother holding all that cash before it ever gets to you. (Kids are not allowed to have big cash in detention centers, btw. So no worry there, really.)
And anyway, Arizona locks up boys for first time possession of porn?? And your parents didn't even hire you a lawyer? Harsh. Wait--- back up--- your 13 year old brother has porn AND a lot of cash? What is that guy really up to?
The best way to escape is to smuggle in a loaded gun when you go in. Can you think of anywhere on your person where you could hide a loaded gun?