TEOTIHUACÁN JOURNALNo, the Conquistadors Are Not Back. It's Just Wal-Mart.By JAMES C. McKINLEY Jr.Published: September 28, 2004 AN JUAN DE TEOTIHUACÁN, Mexico, Sept. 21 - The market in this small town is a warren of streets with canopied stalls and battered storefronts, where one can buy everything from fresh avocados to jeans to a vaquero's saddle. As they have for centuries, the merchants here ply their trade midway between the ruins of giant pyramids built by the Maya and the stone steeple of the town's main Catholic church, which Spanish monks founded in 1548.Now another colossus from a different empire...