I'm not sure if the airlines are going to charge extra for my bike.
The costs can be anywhere from nothing to a fortune. Find out before you book the flight, as it may affect your choice of airlines.
Do you think it is possible to motel it at around $50 a night?
Yes, in some places, but I doubt that you'll be able to average $50 for motels. You'll sometimes stay other places for free or almost free, however, which should bring the overall average down.
McD's is apparently great for wifi too.
Unless you go off the ACA TransAm route, you may find McDonalds few and far between. Most of the towns on the ACA TransAm are too small to justify even a McDonalds.