Yes! You can use this app anywhere, as long as your phone has a data connection (Wi-Fi or cellular).
Calling with Wi-Fi is a much less expensive option. Simply connect to a Wi-Fi network and dial the number you wish to reach. Check out the Rates Page to determine the rate for your location. We recommend you top up your account before leaving the US with enough funds to cover your travel. Your credit card will not work while outside the US.