Problem with that Guardian article is the Spanish section is written by Giles Tremlett, who is their journlist on all matters Spanish and not really someone with their ear to the ground regarding the property market. For a start he quotes that prices have fallen by 27% from peak when this forum concluded that real prices had fallen by something like 40% about 6 months ago (it must be nearer 50% now). So talking about a further fall of 20% is pretty irrelevant – we’re already there!
However I personally think talking about property prices on a national level is pretty pointless anyway, as is talking about the oversupply on a national level (unless you are somehow investing in property on a national scale). Most people are looking to buy in a particular area, and that’s the market they should be researching.