Photo: Negroni Artz By THÉRÈSE MARGOLIS Despite its swank address inside the upscale Artz Shopping Mall in Mexico City’s upscale Colonia Jardines de Pedregal – and the hefty prices that come with that locale – there is a distinctive downhome feel to the newly opened Negroni Artz restaurant. The glassed-in patio give Negroni Artz a