I had a great stay at Karla's, the place is right in the middle of historic centre. I didn't even have to take any metro at all because everything is walkable. Since it's in the main centre, there are uncountable bars/restaurants/shops.
Additionally, Karla was a great host, very friendly and welcoming and made me feel like home. Communications were easy and she was always available on WhatsApp to answer any question. If I come to Mexico city again, I would not even consider living at any other place than at this place again. I'll highly recommend this place.