Excellent apartment on Plaza Santa Teresa. The location is perfect, right near the medieval city walls in the nice area of the city. It's very easy to find and reach from the highways going to/from Segovia or Salamanca. We stayed there for four nights and explored the whole region from Salamanca to El Escorial by car using Avila as a base. It worked very well for us. The owners, Rubén and his wife, don't speak English but are very easy to communicate with and are very responsive using email. We don't speak any Spanish and yet managed fine to communicate with them online using Google translator and in person when we arrived in Avila. The apartments are pretty much impeccable, very clean, brand new and very well furnished. We travel a lot and stay in apartments quite often. This apartment was one the best that we stayed in. We booked one bedroom apartment on Booking.com, but were graciously upgraded by Rubén and his wife to two bedroom for the same price because it was available at the time.
You can find restaurants, cafe that serves coffee, sandwiches and sweets and some stores right on the plaza. Check La Bodeguita de San Segundo bar (located within five minutes walk from the apartment) with their delicious tapas and their extensive and inexpensive wine list. There is parking garage under the apartment building but it's expensive, around 18 Euros per day. You can also park on the streets near the plaza. We managed to find a parking spot withing 2 minuets walk from the apartment every night. All nights are free and during the day you pay something like two Euros per four hours.
I highly recommend these apartments especially to those who want to use Avila as a base and explore the region to the North West of Madrid by car. It turned out to be very easy for us, much more flexible and even cheaper then to make day trips from Madrid as many people do.