Just as described, Santiago's artistic apartment/loft is in a nice, quiet area close to the park Chapultepec.
The apartment itself is comfortable, with blackout curtains that help you catch up on sleep and enough space to hang out inside on the couch or outside on the patio before heading out into the city.
Location-wise, it's in a quiet and lovely neighborhood, with several coffee shops and breakfast spots in walkable distance. This isn't the bustling Roma Norte, which is about a 25 minute walk away (so don't expect to be able to just pop out to a bar for a nightcap), but it is a very cute area. Quiet, safe, with lots of dog owners.
And the best part: a comprehensive guide to the surrounding neighborhood restaurants and museum provided by Santiago himself.