Dinah,
First class buses are comfortable, the seats recline -- many people sleep on them. You will need to bring your own blanket and pillow. They have bathrooms. Executive class is even better, with somewhat larger seats and usually fewer stops. They show movies, which can be loud, although on my last couple of trips, they handed out headsets and turned off the speakers. I'd take earplugs just in case.
See Larpman's website for more information:
http://www.larpman.com/transportpages/b ... buswi.htmlI've never bought tickets online. I usually try to buy them the day before at the bus station, but in many instances, I've just shown up an hour or so before scheduled departure and have always managed to get a seat.
...but, since you only have a week, I'm not sure I'd be quite that cavalier. I would plan to travel from Nuevo Laredo rather than Saltillo or Monterrey. There are far more scheduled buses from there.
I would also consider taking the bus to Queretaro, which will also give you a lot more choices. From there, it's a short 1 hour ride to SMA. I've done it several times and even if you don't get on a first class bus, it's an easy trip. In the worst case, a taxi from Queretaro to SMA is a lot cheaper than one from Leon. Turistar, Transportes del Norte, Estrella Blanca, Omnibuses de Mexico and Estrella Blanca all have routes between Nuevo Laredo and Queretaro. The trip is about 10 hours, maybe a bit more, depending on stops.
Estrella Blanca has their schedules on their web site:
http://www.estrellablanca.com.mx/It's in Spanish, but pretty easy to follow. Select your "origen" and "destino" and click "buscar" (search). This will show you departure times, "hora salida". Click "ver" to see details. "Clave" is the route number "Hora Llegada" is arrival time and "Hora Salida" is the departure time, shown for each stop on the route.
Al