My favorite neighborhood in Mexico City is Coyoacan. It's primarily residential, with tall tree-lined streets and plenty of quiet cafes and gardens. But there is a ton to do here as well! The Frida Kahlo museum, Trotsky Museum, the Artisanal Market, and many more attractions are located in this area. It is very quiet at night - so is fantastic if you are traveling with young children or older family members. Easily walkable - we didn't need a car if we wanted to stay in the neighborhood. Tons of markets, cafes, bakeries and taco stands. Fantastic shopping and the friendliest folks. The only downside is that it is 12 km south of the center city which can mean being in traffic congestion if you are trying to get to any of the northern neighborhoods.