The culinary trademark of Ruggles Grill [903 Westheimer, (713)524-3839] and most of its siblings [Bistro Latino, 711 Main, (713)227-9141; Enron Field, 333 Crawford, (713)259-8080; and Grille 5115 in Saks Fifth Avenue at the Galleria, (713)963-8067] is the massive medley of Southwestern-style vegetables that accompanies every entrée. But only one thing…