When it comes to bond, federal court is substantially different than state court. There is no "cash bond" in federal court (except in VERY rare cases). Either the government moves to detain pre-trial or they do not. If they move to detain, then there will be a detention hearing held and the judge will either order them detained, or let them out on their own recognizance. If released, then they will be under supervision of the pre-trial services office. If they screw up on pre-trial release, they will likely be detained.
A lot of this depends on what they are charged with as well if the government will move to detain or not. As far as lawyers go, if they can't afford one they will either be represented by the federal public defender's office or a private attorney will be appointed to represent them.
My reasoning is that if they skip their court appearance, they will be wanted by the FBI.
If they skip their court appearance and are arrested again at another riot, then they are a repeat offender and a flight risk.
That should mean automatic detention.
These are kids who disregard the law, so I'm guessing they will opt for Door Number Two.
-PJ