By far and away the fastest way to get an internet connection at a home in Marbella is to pop in to a Vodafone or Movistar shop and get yourself a contract for a 3G/wireless modem.
(Note, you have a PCMCIA (card) option or a USB option, even if you only have a notebook, it's a good idea to get the USB one, as you can use it on any machine - let's say you are out at a meeting and their internet access goes down, you can simply plug the modem in - let it autoinstall the files, and away you go!)
This is by no means the cheapest, or the best way to get connected long term (as these cost a great deal of money as compared to normal connection methods such as ADSL). This is however, the fastest.
Regards,
Eric Marsella
MARS I.T. Services
www.marsspain.com / +34 667 698 833