ATT international plan will be 50 cents/minute plus taxes. Not the cheapest, but easiest. You can set this up on the ATT website.

Or as stated above..

Download the skype app for your phone or tablet or both, you call from your phone/tablet to a landline. If you call to another tablet you can see each other. But the video really slows down the connection.

Many places on Anegada have wifi, you can setup Skype before you go and use it before you go. Calling via Skype to a house phone will be about 6 cents/minute, but as stated above you will need to setup a skype credit. Calling to another device will be free.