Both options are good for making calls, but renting a cell phone has the advantage of allowing you to receive calls and also to make calls wherever you are (as opposed to having to find a phone from where to dial each time). Calls will be cheaper from a phone card, by about as much as 60 cents per minute for international calls (rental phones can charge up to $1 U.S.D. for international calls and $0.30 for domestic calls).