We stayed at Ana's house for 3 months and loved it. It is very centric, in a safe, quiet neighborhood and has 2 supermarkets, a fresh produce store and 2 pharmacies within a 2 block radius. The best supermarket is actually only half a block, so shopping for food is painless.
It is 1 block away from a plaza that has a BUNCH of bus stops which is really handy and you can get anywhere easily starting there. There are also 2 metro stations in opposing directions, about 7 mins away. It is relatively close to the main train station (Atocha) which makes traveling easy too.
The house itself is cozy and comfortable. It has air conditioning in every room, although we only used it during the hottest days, as the nights were quite cool with the windows open. At first glance the kitchen seems tiny, but it is really very functional. We cooked all our meals and managed very well. She has a well equipped kitchen despite its size. The kitchen includes the washing machine. The clothes line for drying is out the bedroom windows. Madrid is so dry, the clothes dry SUPER quickly.
Ana was really helpful during our stay. She brought us plenty of fresh sheets and towels when we got there. She came over and helped sort out a loose connection with the tv antenna, and got the dvd player running. She was also available by telephone or whatsapp to answer any questions.
If you have small children be aware: the windows slide open very wide, very easily. We took window stops to limit how much the window could slide open. I highly recommend bringing your own (non permanent) childproofing. We also took cabinet locks to keep the kid from opening the doors to the cupboard under the sink which are full of cleaning supplies.
If you have kids, there are several small neighborhood parks very nearby. There is also a carousel one block down! But the best part is that you are right across the street from a gigantic LOVELY park called El Retiro, complete with duck ponds, rose garden and museums. Retiro also has several children's play areas within the park.
During our stay we felt very lucky to have chosen Ana's place to stay. We thoroughly enjoyed it.