We loved the location and layout of Luisa's apartment. Close to the main plazas in one direction; and the park ("river") on the other. It's super clean and accommodating and the view of the Church is wonderful.
Our taxi driver couldn't easily locate the address (we ended up on the other side of the Church), so you may want to get clarification from Luisa before your arrival. As others have mentioned, it can be loud (footsteps above + street noise), but it's really not bad. We actually stayed in a different neighborhood in Valencia two years ago, and the noise was much worse (so chalk it up to the life of the city ;).
We highly recommend Luisa's place to you.