Thanks, Londinense! So why is using the bus system better than renting a car? Is traffic particularly bad?

To be clear, I'd never dream of trying to see all the places I mentioned in one trip. Those are just places that looked interesting.

There is nothing wrong with renting a car, but bear in mind that it can be quite expensive, when the mandatory insurance is added. You are planning to visit large cities with a population of a million and more and negotiating their one-way systems can be quite a challenge. How good is your Spanish? Will you have GPS on your phone? Travelling between cities will mostly be on toll highways, so the charges have to be factored in, as well as parking charges when you arrive.

Buses are fast. albeit not as fast as trains in Europe, frequent, comfortable and relatively inexpensive.

Depending on your itinerary you can always rent a car for a day or two at your destination to visit the surroundings. In the Oaxaca valley for instance. However, even there, hiring a car with driver is probably a better option.

Indeed, all of those places have their interest, although I am not a fan of Cuernavaca or Taxco. But others who frequent these forums like Taxco.

What about those towns aren't you fond of?

It's more than 10 years since I was last in Cuernavaca and closer to 20 Taxco, so things might have improved. I found both noisy, polluted and clogged with traffic.

There are plenty of others that I enjoy returning to, especially Puebla and Oaxaca. Querétaro and Guanajuato are both close to San Miguel, so I visit them quite frequently. I have only been to SLP and Zacatecas once and would happily return should the occasion arise.. All have attractive historic centres, even when they are surrounded by huge urban sprawl.

From my understanding, Cuernavaca has become quite industrial and has lost its charm. Taxco is a gorgeous town but is very touristic - shops selling silver jewelry everywhere.

I've traveled a lot around Mexico over the years. A car rental is certainly a good way to do it, but, as previously mentioned, it isn't as cheap as it might appear at first. You will get online quotes that appear ridiculously cheap but you end up paying many multiples of the quoted price due to compulsory insurance. And it is advised that you purchase it as it may keep you out of a Mexican prison if you have a mishap. Look around the forum and you will find many other posts regarding car rentals and the bitter feelings that come from the experience. There is also the problem of corrupt police shaking you down for hefty bribes.

So consider traveling by bus. They are very comfortable, even luxurious. Far superior to buses in the U.S. or Canada and probably Europe too.

As for an itinerary, I would recommend a loop that takes in many of the colonial cities. Querétaro, San Miguel de Allende, Guanajuato, Morelia, Patzcuaro, the Monarch Butterfly sanctuaries (if you are traveling between December and March), Mexico City. You could then travel south to Oaxaca via Puebla. Then some beach time on the Pacific coast in either Huatulco or Puerto Escondido (depending on whether you like upscale or middle of the road.) This area is guaranteed almost perfect sunny weather while the Caribbean side has more rain and possible seaweed invasion of the beaches.

Way before I moved here permanently my choice for a 2 wk jaunt was Mexico City/Oaxaca and environs/coast there. This could be extended to be Mexico City/Oaxaca/Tejuantepec peninsula which is wildly awesome into Chiapas, Chiapas sites then back via coast.

I´d choose one or the other, south or north. North I´d go Mexico City, Zacatecas, maybe SLP and the Huasteca region, Guadalajara and end in Pacific Coast like San Pancho.

Great information. Thanks everyone!

If it were me on a 3 week trip, I'd take the southern route:

Mexico City: 5 nights

Puebla (2 hours by bus): 3 nights

Oaxaca ( hours by bus, a beautiful ride): 5 nights

Puerto Escondido or other Pacific beach town (a short hop by plane): 5 nights

Mexico City (flight from the Pacific coast area): 2 nights