It is off the toll way but it is worth the drive, it is between Acapulco and Mexico City. There is regular bus service to the town from Cuernavaca by Estrella Blanca.
There are also buses there from Mexico City from the South Bus Station (Autobuses del Sur). A one-way ticket costs $130 pesos and they usually leave every half hour. The bus will take you through very scenic mountain views and drop you off in the middle of the town. Since it is a mountain town, you can either walk uphill to the Zocolo (square) where many shops and the famous church are, take a taxi, or any bus that says "Zocalo".
The last bus out of Taxco back to Mexico City is 8 p.m
