Or VODAFONE who have several services, none need a land line or connection or dealing with telefonica!
For 39 euros per month (plus iva) you get a modem that you place into a usb point, it installs itself and off you go - fully useable anywhere there is coverage, cafes, bars, hotels etc!
They do a landline as well for 15 euros per month which includes free calls to any landline in Spain - this landline comes over the mobile phone network so you can carry it with you anywhere too! Great if you are going to move house etc.
They also do an adsl fone package for in the house, all wireless but depends on if you have coverage as its relatively new in being set up
I managed to finally extract myself from telefonica late last year and am solely with vodafone. They are not perfect but there customer service is a much better level than anything I have experienced before and they have actual people you can talk to.