Rick Bayless might be best known for bringing Mexican fine dining to Chicago with restaurants such as Frontera Grill and Topolobampo. He also won Bravo's Top Chef Masters in 2009 and cooked for President Barack Obama during a state dinner to honor Mexican President Felipe Calderon and his wife, Margarita Zavala. Yet on Saturday evening, Bayless focused his attention on the 300-plus people who filled a tent in the parking lot at Westfield Old Orchard Mall in Skokie.  One of the dishes Bayless made for his audience was mango guacamole or guacamole de mango. His new book, Fiesta at Rick's, has a…