If you've eaten at this Eastside Mexican food mainstay, you know Mr. Mesa's handshake: warm, perfectly firm, heartfelt but not overlong. And his gaze - he looks straight at you, he remembers you. You return, Mr. Mesa recognizes you. He's almost always there, circulating among the tables, and when he shakes your hand, you know you're not just a stomach with a wallet, you're his guest. As with his famous Don Juan taco, you may just want to use both hands.