Either option works, although phone cards will not allow you to receive incoming calls. The rate-per-minute will be less expensive with a phone card than with a cell phone rental. Phone cards are available for purchase throughout Costa Rica in small convenience stores and supermarkets. These phone cards can be used from regular landlines, cell phones, and pay phones.
Cell phone rentals are more convenient, but the rates can be up to $1/minute for international calls and $0.30/minute for domestic calls.
The most cost effective option for people looking to have the convenience of a cell phone without expensive fees is to purchase a pre-paid SIM/GSM chip from ICE that can be inserted in an unlocked cell phone that uses SIM/4G technology. The rates for the ICE pre-paid SIM/GSM cards are about $0.30/minute for international calls and $0.03/minute for domestic calls.