We did not check out by 11.00 am (we were running late) and this is our fault. However, the host showed up at the entrance of the apartment at 11.30 am with the new guests without a heads-up. We would have preferred a message from the owner, advising us to speed up the check out process.
Lastly, there is no possibility to leave your luggages inside the building after the check out. This could be useful if you have to take a flight from Valencia airport in late afternoon.