Good luck with everything! The apartment looks great, and I'm quite sure you'll find it a perfect base for exploring the city. The visitor comments in Spanish are almost panegyric regarding both the apartment, the location and the helpful owners.

You'll be doing your grocery shopping in the Gros district where I used to live. Gives a nice everyday feel a bit distinct from the "extravagancas" on the other side of the river. Besides, as you know, many of the best pintxos bars are on "your" side of Urumea. You will be very close to El Lagar, their pintxos are always on the top ten list and they specialize in a vide range of wines by the glass.
http://www.todopintxos.com/bares/bar...bar&id_bar=117

Just happy to help with follow up questions.