The fact that the stop is a Package Express stop does not typically mean you have to go with Package Express. My understanding is that Package Express is supposed to be using the bus as a shipping service when you are not riding as a passenger. You should still be able to just check the bike as baggage if you are travelling on that bus. I say "should" because the dog is always an adventure and you seem to get a different story at every station. Once here in Tallahassee a friend was told that they didn't take bikes at all (his was boxed up). After a bit of pleading his case they relented, loaded the bike, and let him board.

When I have ridden the dog I have sat next to drunks, just released convicts, and other "interesting" people. As I said it is always an adventure and I have mostly stopped using the dog.

"Take the Greyhound
It's a dog of a way to get around
Take the Greyhound
It's a dog gone easy way to get you down"
Harry Chapin "Greyhound"