It depends on your meaning of ‘bottom out’.
If you mean when property prices stabilise then that’s anyone’s guess. What complicates that in Spain is the law which forces mortgage holders to repay the entire debt plus costs even though a property might have been repossessed.
What happens in practice is the debtor sits tight pays interest only to the bank and hopes to sell it for what they owe to get out of trouble. So asking prices don’t drop, the property doesn’t sell and the market is struck. Low offers if there are any get rejected.
This log jam is usually broken when the debtor can’t even manage the interest only payment and is foreclosed. That takes time.
If you mean the Spanish economy bottoming out and starting to recover my best estimate is without any substantial EU/IMF stimulus anything up to 5 years or even longer. The performance of the global economy is crucial to that and all educated predictions are that in 2013 it will substantially worsen.