If going to Spain for 3 months what is best option for internet use on my laptop should I buy Stick Modem from Vodaphone Ireland or is there another way to go about it in Spain,
Buy a stick modem there but ensure you are not tied into a contract. I have found better value and coverage from Movistar (Telefonica) but there are a variety of companies operating.
Jonocon has the best advice. Buy a usb modem and sim card in Spain. Using an Irish purchased modem will probably involve you in heavy roaming charges. If you have an unlocked irish modem you will only have to purchase a Spanish sim card. I have used the Vodafone company in Spain, and find charges reasonable.