Your resource for mobile choices.
If possible, get a SIM card through a local provider so you can use data in Spain inexpensively. This will come in handy when you are navigating and communicating while you're out and don't have access to Wi-Fi.
Orange, Movistar, and Vodaphone provide cheap data and phone plans (15€ - 60€+ per month). With a Spanish phone plan, your phone will also work in any EU country without extra cost.
Please note that you might have to unlock your phone in order to switch to a Spanish SIM card. We recommend contacting your phone carrier prior to arriving in Spain to explore your options.