On Sunday afternoons around 4 p.m., I leave my home in the center of Guanajuato and stroll over to a nearby park called Embajadoras. The market there closes early for Sunday comida, but families are still hanging out, kids are shrieking, old ladies are chatting and the vendors are doing a healthy trade. This park, with its inviting benches, trees and shrubbery, is a classic example of a “third place,” a term coined by the sociologist Ray Oldenb…