Best Mobile/Sim Card for use in Ecuador/Galapagos Islands

[100 IAN]

Teenage son is off to Ecuador & Galapagos Islands for a 2 week working 'holiday' and we want to be able to stay in touch with him.

Where's the best place to get a sim for his phone so that keeping in touch isn't going to bankrupt him/us?

[100 IAN]

He's doing a student working program helping out in a school and then a turtle project.

It'll be a great experience for him and I'm very jealous, would love to be going with him but sadly not.