Getting to Cuernavaca is fairly easy but beware the traffic in the Mexico-Cuernavaca-Acapulco tollway on Friday and Sunday afternoons. Many visitors tend to travel those days and you might spend more than 2 hours on the road. Plan accordingly or choose other days for your travelling.
By plane
Viva Aerobus has started offering very cheap tickets, around $45USD, when flying from Tijuana or Monterrey, though the airport is not that close to Cuernavaca. Expect to pay around $25.00 USD for the taxi to Cuernavaca's central square.
By car
Take the Mexico-Acapulco expressway south from Mexico City for an hour and a half to two hours from the international airport. The toll road costs $85 pesos or there is a free road which is less well maintained and is primarily single-laned.
By bus
Several bus companies operate routes to Cuernavaca. Buses run from Mexico City's main bus stations in the North, South of the city and Airport. Bus station at the Airport is well advised and to travel to Cuernavaca you can use Pullman de Morelos (http://www.pullman.com.mx...) They will take you direct from the Airport to Casino de la Selva Terminal in Cuernavaca. It is also possible to catch a bus from the main toll plaza at the south of the city. Buses run on average every 20 minutes and tickets cost around $68 pesos to $135 from the Airport. Pullman de Morelos runs the most frequent routes. Buses are modern and safe and come equipped with air conditioning, toilets, and a movie during the trip. When there is no traffic the trip takes around 1 hour, 2 hour from the Airport. Once within Cuernavaca, the bus will drop you off along the route wherever you like, except the one from the Airport that is non-stop, It's called Ejecutivo Dorado.