Margaritas, spicy guacamole--and murder--are among this year's preparations for Cinco de Mayo in the second Santa Fe Caf? mystery novel. Tres Amigas Caf? chef Rita Lafitte is busy baking her green chile souffl?s and chocolate flans for Cinco de Mayo. If only her friend Linda, the daughter of Rita's octogenarian boss Flori, could get into the festive spirit. Linda's cart, Tia Tamales, is losing business to Crepe Empire, the hottest food cart in Santa...