This question came up recently in our forum. You can check out this thread for more detail: https://www.twoweeksincostarica.com/question/whats-the-best-way-to-change-money-in-cr/. Basically you need to bring an unlocked quad band phone to Costa Rica and get a chip/SIM card at the airport from Kolbi. You can then pay a few dollars for a prepaid phone plan and add on to it later if you run out of minutes. You can recharge it at lots of small grocery stores throughout the country- just look for the Kolbi sign. You can also get an Internet plan if you want to have it for on the go. I believe they’re priced based on speed and are very affordable (we paid $20/month for 2 MB).