I second the recommendation for visiting the area around the Leon/Guanajuato airport, known as the Bajio.

It's a major agricultural and industrial area. I think it's the GM plant that's located right by the airport. My first impression of the area was that it looks like it should be one of the richest areas in the world.

The climate is wonderful. You're at about 4-5000 feet.

Secondly, Guanajuato and the neighboring state of Queretero are 2 of the least corrupt and best governed states in Mexico. Crime is not a big factor here.

San Miguel de Allende is a mini Santa Fe, New Mexico ... yes, it has a large expat U.S. community. Guanajuato (the city) is simply the most beautiful town in Mexico. It's a former silver mining boom town that has transformed itself into a college town and living museum. Leon is the leather (and shoe) capital of Mexico. People come from all over to buy wholesale here. It is not a particularly attractive city but it is one of the few Mexican cities that has a real go go feel to it.

As for buses, there are excellent services throughout the area. My favorite line is Primera Plus. For longer distances, ETN offers VIP service (e.g. 22 seats on a bus, 2 X 1 first class type seating).

By all means, you can take the bus to PVR. Personally, other than changing buses in GDL, I'd regard that city as too unsafe to visit.