I lived there for a summer in 2003. Center is walkable, yes. Centro Historico, and to Condesa, Roma, etc. To the south, Coyoacan was lovely if heavily touristed. I lived there. Kahlo & Trotsky houses, the Plaza, etc. Slightly to the south of that, the central spaces of the University City are classic midcentury modernism. Subway system is cheap and extensive. Luxury shopping is not a strong point. Wealth is in the northwest quadrant of the city, starting in Polanco and heading into the hills. The international store branches are on Avenida Massaryk, but Mexicans with more money will buy abroad, and you should too. For more detail on local strengths, Monocle magazine (led by Tyler Brule, Wallpaper mag founder) did a Mexico edition last year, online here:
http://www.monocle.com/sections/edit...s/Mexico-City/ The leading map publisher is Guia Roji:
http://www.guiaroji.com.mx/ Get one, be it little or large.