I live in the DF, in La Condesa. It's lovely, green, more or less bohemian, and still in the city--no large open spaces, but we really like it.
There are some really nice areas in Mixcoac, too, just south of DF's Centro Histórico--houses with big yards, etc.
Farther out, I'd say San Jerónimo, Tlalpan, parts of San Ángel, and (way out) Valle del Bravo. Here's a real estate company with listings for Valle del Bravo: http://www.century21global.com/...9xico/Valle-de-Bravo
Take a look at http://www.vivanuncios.com.mx
, too. Using the parameters that the site offers, put in the locations I suggest (and any others that others suggest) and see what you find.
Best of luck in your search--you're going to love it here.