You're going to be on holiday. How much time do you think you'll be spending talking to people back home? Depending on where in the US you'd be calling, there'd be a time difference between 13 and 16 hours. Essentially you have 2 options: #1: You could come here with your American smartphone, equip it with applications like Skype, OTO, and Kakao and use those applications wherever you can find wifi (wifi is widely available here)... OR #2: You could get a drop phone from a kiosk at the airport - usually they only have phones that can make calls and send texts, but it's possible that they might have smartphones for rent, or possibly even for purchase, and you can use that phone whilst here. If it's hooked up to the Korean mobile network it will also allow you to make local calls here, and if you purchase a data plan, you will be able to access the internet and use your Korean mobile to call friends and family back home. Lastly, you could also look into renting a wifi egg so that you can connect your own American smartphone to the internet whenever and wherever you want, but I'm not sure that they make those available to people visiting for only a short time.