Hi Barbara,
If you get the AreaNet@home connection then you don't need to pay for the phone line so there is no monthly charge.
So just need to pay for the modem, either the fixed or wireless. See userfiles/file/ptan_files/guiadeservicios.pdf You can get the cards from the sports bar, and i'm told the supermarket should have thme too.
To get it installed you need to contact Polaris Telecom
Call Center Telecom
Email: info.telecom@polarisworld.com
Tel: .+(34) 902 500 424
Fax: .+(34) 968 011 375
One downside is it doesn't work at the moment, should by late Oct, but as Mick says below on the good side they seem to be offering you a free connectivity at the moment until they get the Areanet part sorted.
Phil