The reason they weren't worried (Sam was worried that teh whole thing would backfire and they'd be trapped while Dean was his usual over cocky self), is because their dad's friend worked at that particular dentention center and everything that happened was part of Dean's big plan to get rid of the ghost.

Now, if they'd ended up in a different place, one outside of the plan, then they'd be screwed because there's no way that a public defender would have been able to get them out of jail. And if they didn't have someone to assist in their escape, they'd more than likely be trapped for a longer period of time.

They also never expected the FBI to come into it as quickly as they did, which almost screwed up Dean's plan.

So I think your fic should be fine, but that's just me.