Mostly illegals ride these long haul buses. So sorry.
I recently rode one for the first time. There were actually a lot of soldiers on my bus, and at every station we stopped at. They were privates and in uniform - I think their first leave after basic or something like that.
And a lot of people on their way home from prison - I think they get a bus ticket on their way out. The first guy I talked to had just gotten out.
Actually no illegals that I could tell. At one station, a guy was drunk or stoned, and Greyhound called police in a nanosecond. So I think the prevalence of police may keep them away.