Marcia was an amazing host. She was very accommodating to our early arrival and late checkout. The apartment is a very modern, clean and spacious loft with three large windows that open up to the Main Street three floors below. There is a Starbucks, a great taco shop and a convenience store all only steps from the building entrance. 24 hour security is great, the guards always friendly.
10 minute walk to the Cathedral and Zocolo, 5 minutes he other direction to Bella Artes. The metro is right near Bella Artes. We took Uber (which will pick you up at the main door), it's cheap, safe and easy to use ($5 UberX or $10 Uber Black Car, one way from/to the airport, a 30 minute drive).
The area is busy, two major shopping/walking streets, but the apartment doesn't get much noise at night.
Lastly the rooftop deck is great for having a beer and watching the street traffic below.