GUANAJUATO, Mexico — Houses painted hot pink, bright orange and cobalt blue tucked into cobbled alleyways too narrow for cars. . Sidewalk cafes, shady plazas and strolling street musicians. Spain, Italy, France? It would be easy to mistake this university town in the mountains of Central Mexico for a medieval city in Europe. Substitute the easy-on-the-wallet peso for the pricey euro, and nearly year-round springlike weather and you've got a bargain travel destination where the U.S. doll...