6weeks in USA whats the best sim option, data is number one

So, I will be visiting America for 6 weeks. Middle Jan-February 2014

I will be staying with family that do not have internet access.

I'd like to jus pick up a sim card and use my phone with wifi/usb tether as my internet connection

I dont care about minutes or text messages as everyone I know uses either KaKao or Hangouts

What do you guys think? Your help would be greatly appreciated.

More info

I am a US citizen

I have an iphone 5(cdma version) and a Galaxy Note 3 LTE-A (SKT version)