Zacatecas in July when the
International Folkloric Festival arrives is amazing. Actually any place in July (when Mexico travels and the families are out and about) is amazing. Zacatecas has
amazing colonial architecture and the most incredible
church facade we've ever seen in Mexico. You will find the
Alhondigas (is that spelled correctly PDS?) in Zacatecas - (oops - it is in Guanajuato - sorry) and the
museum there is amazing, especially if you've been to Hidalgo's home in Dolores Hidalgo. Zacatecas also has a mine with a very nice tour in a coverted coal/rock car. The
Teleferico is touristy but still a pretty experience and amazing view of the city.
Just north of Zacatecas you will find lovely little Jerez and La Quemada, one of the most beautiful Aztec ruins we've been to.
Pictures
here and
here
Guanajuato is lovely and quaint. The streets are itsy and the
catacombs really interesting but once is enough.
Guanajuato has
Diego Rivera's childhood home and well worth a visit. There are amazing
mines at the upper part of the city and it is well worth a poke around up there.
The drive from Guanajuato to Dolores Hidalgo is gorgeous, as is much of the Bajito. They also have the mummy museum, a beautiful hacienda and I think I broke my brain because I've forgotten what I was going to post.
I would also recommend Queretaro, the Huasteca Potosina (if you're into nature), Xalapa/Jalapa, Coatepec, Mazatlan (they are finally rennovating their downtown, but it would be down on my list unless you had a car you could use to visit some of the neighboring towns), Bernal (we haven't been there yet, but it is on my list) and believe it or not, DF. We haven't been to DF yet, but I really think it would be worth the while. Otherwise, stay in Queretaro and take a bus in. I think Queretaro is really your best bet - it is a lovely walking city and both SMA, Dolores Hidalgo, Bernal and DF are all within short(ish) driving.
I gave up trying to link photos to text, but if you're interested just go to my Flickr and search on Guanajuato, Jerez, Zacatecas or whatever. I tried to use tags pretty reasonably.