Lena's apartment is in a great location. Lisbon is a relatively small capital city, so it is easy to get the bus or metro into the centre within 10 minutes. It also means that if you want to see how locals live and eat, then this is the place to be.
My tip is to try the ice cream at FIB - https://www.facebook.com/GeladosFIB/ It was great and the staff were very friendly