You can unlock your phone and grab a prepaid usa sim card from tmobile or At&t. Or if you have some time before you leave you can get a sim mailed to you from one of their mvno like red pocket or straight talk.
To call home on those plans you can use Google voice via the app (android) or through their html5 interface. (voice.google.com).
I don't think koodo will unblock a prepaid phone but you can normally find unlock codes on ebay or gsm libertym.com