I spent a lot of time in Queretaro, and love the place. Terrific hospitality, many good restaurants, and wonderful weather. Not far away is San Miguel de Allende, which is full of artists from all over the world. It also has good restaurants and many galleries to visit.
The road that connects San Miguel to Guanajuato passes through Dolores Hidalgo, a town with an active ceramic industry. Great place to shop for tile, dishes, etc.
Guanajuato was formerly a silver mining town, and has unusual topography. It's known for its caves filled with mummified corpses. Quite unusual.
I've had many great experiences in Mexico, and highly recommend it.