Here is my 6-day itinerary, including where I stayed, what I ate, and where I visited:
Day ONE
Arrive at Mexico City airport in the late afternoon
Take an Uber to your Airbnb in Hipódromo
Stroll through Parque Mexico
Eat a trio of tacos al pastor from a nearby taqueria
Stop by Neveria Roxy for old-school helado
DAY TWO
Grab an Uber to Bella Artes
Go across the street to Sears to the cafe on the 9th floor
Have an espresso and pastry while enjoying the view from the balcony
Walk to Centro Histórico
Spend a long afternoon walking through the ruins of Templo Mayor and marveling at the Diego mural at Palacio Nacional
Find some late night elotes in the zócalo
Day THREE
Arrive at Casa Azul by opening to avoid crowds
After, take a walk over to Cafe El Jarocho for a mocha
Sit at any counter in the mercado for a delicious lunch
Take a long metro ride back north to Chapultepec
Roam the expansive Chapultepec, including the castle atop the hill