The flat is within walking distance from the centre through nice streets, 15-20 minutes maximum. Peaceful area with less explosives than in the centre. (We were there during the week before Las Fallas. Be prepared with ear protection if you walk in the centre since the locals throw explosives like bangers which sound like car bombs. Not nice).
Good super market in Mercadona. Strong wifi, internet connection without problems. When we took showers the floor got wet outside of the cabin. Thin walls, but not a big problem.