What time does your flight get in? There is a airport commuter bus schedule and instructions on where to find the bus online at http://www.cuernavacainfo.com/bus.html Sometimes you have to wait a bit for a bus, if the next one or two happens to be full. And if your flight gets in late in the evening, you might want to just arrange for a private driver to meet you at the airport. If you get stuck staying in Mexico City, it can be expensive, especially at the hotels that are connected to the airport. Most schools offer a pick up service and I've used the one offered by the cuernavacainfo website.
I know that Instituto Chac Mool Spanish school in Cuernavaca has a popular program for mature students and they have lectures and workshops with topics such as traveling alone in Mexico, where to travel, getting medical care in Mexico, retiring in Mexico, etc.