The Fritzie Guide to Mexico City
My favorite neighborhood in Mexico City is Roma Norte, which is right next to Condesa. It's a little rough around the edges, but has some of the most beautiful colonial architecture. It's evolved similarly to Williamsburg in that a bunch of artists started to move in and opened great bars, restaurants and shops, but it's prettier than Williamsburg and still has a lot of local artisans at the flea markets and farmers markets. Lots of local boutique shopping along Orizaba with lots of good finds from Mexican indie designers.
Condesa is a more polished version of Roma Norte. It's been considered trendy for a long time and has good eats and cute hotels. It can be hard to tell where Roma Norte ends and Condesa begins.
Polanco isn't far off and is the more commercialized high-end district. Think 5th Ave or SoHo. Some decent restaurants, but you won't find much that you can't find in the U.S.
Beyond those three, most of the stuff you'll want to see is scattered all over the city and D.F. is really, really big with a mega traffic problem, so prepare to account for that.
Remember - take the good ubers because they're cheap (I think it's still called Uber Black?)! Avoid traditional taxis if you can. They'll be quick to scam you. Less quick to kidnap you, but it does happen occasionally. Kidnapping is weirdly a thing in Mexico, though I've never been kidnapped and I'm pretty reckless.
AND DON'T DRINK THE WATER! USE BOTTLED WATER TO BRUSH YOUR TEETH! MOCTEZUMA'S REVENGE IS REAL AND IT IS BAD! Water is fine for washing your hands and showering.