Not sure yet, but pretty sure it won't be Ajijic.
Ajijic has some nice features, but some downsides also. We really liked Guanajuato - nice old university - having an Impressionist exhibit there this summer - Monet, Chagall, Van Gogh, and others. More cultural opportunities there with the annual Cervantes festival and other theater and music.
I suspect we will move somewhere in central Mexico, rent and explore the country for a year or two before buying