This is a great suggestion. Trains used to be cheap and easy in Europe, they are no longer the cheapest or easiest option in many cases. We need to consider options.
I have been all over Mexico by bus. It was a recommendation of a Mexican friend when I asked about driving in Mexico.
Although not comfortable for long trips, they were great for our shorter trips. The quality of first class was the same or better than a charter bus in the US, no chickens in your lap and much better than greyhound.
I have also done day tours by bus in Europe, the service is reliable and the cost is very reasonable.