You have a few options:
.If you have a tri-band/GSM phone in Maryland you can call your phone company and inquire about the rates to call from Ibiza.
.I usually bring my tri-band/GSM phone which I bought in Europe. I purchase a SIM card from Movistar in Ibiza and add credits/minutes to the SIM card throughout the vacation.
.Last summer my friend bought a Tri-Band/GSM Phone from Vodaphone in Ibiza for approx $60-$65 U.S and it came with phone credits, as the credits/minutes ran low he just paid more $$ for additional minutes.
>I will recommend having a phone in Ibiza. You can send SMS (text messages) to people you meet on your vacation to arrange hang out times/spots, you can call and make dinner reservations at your favorite restaurants, and you can call home or have friends/loved ones call you at any time.