As someone with extensive experience of ADSL in Spain may I warn you about Telefonica; this is obviously only my opinion but they are definitely not to be trusted- my phone line was not working for 3 months because their idiot engineer installed it wrong and every month my landline made ONE call to a mobile number- even though I had silence instead of a dialtone on my phone the whole time- thus allowing them to say I was using the line and therefore had to pay for it. this cost me about €200 when they should have been compensating ME for not giving me the line after I ordered it. Nice eh? Be careful....
Mind you nearly all landlines in Spain are owned by TF so even if you get your internet from another provider it is hard to avoid them. I thought I had managed it when I signed up for the WiMax service from Iberbanda, but then discovered that TF owns 51% of Iberbanda.
The truth is that Spain is crying out for a non-incompetent/non-greedy internet provider but unless people here stop putting up with their tricks it is not going to happen. I have heard bad things about all of them, even Ono which is the only one with its own infrastructure, but I hear Jazztel are particularly bad. YMMV.