Stayed at Casa Berlin for 12 days with a group of 5, two teenagers, two adults, and 90 yr old and place worked out fine for us. The wi-fi worked great for 3-4 devices all on line at the same time. The master bedroom is great and the other 3 beds are okay but not very roomy. However, if you are going to be a tourist then it shouldn't be a concern. Two of the bathrooms are roomy but the one upstairs is very tight but suitable for showering. Water pressure is great so no problem there.
I would highly recommend this place. It is away from the main hustle and bustle of Mexico City and quiet at night compared to other parts of the city. Just around the corner on Londress street is great place to have breakfast, La Panera and right across the street from there is great bakery and coffee spot and also fantastic place to get Tamales. Also you can catch the very cheap($5 pesos) local buses($.35-.40 cents US) called the Peseros on Londress St that will take you right into the Coyoacan town center. They also pass right by the Frida Kahlo museum but that is only a 10 minute casual walk from Casa Berlin and since you are walking don't forget to go visit The Trosky house, now museum and see where one of the giants of the Russian revolution met his end. There is a lot more to write down but Casa Berlin is well situated for visiting Coyoacan and the rest of Mexico City and by the way it is a relatively safe part of greater Mex City. I have certainly recommended this spot for the other large extended part of my family.