Originally Posted by
moondog
Just be sure to suppress its desire to place calls over your cell network if it decides your signal quality isn't up to par (there's a setting for this), and its often necessary to tunnel through a US server.
In Google Voice, go to settings, make and receive calls, prefer WiFi and data when traveling internationally to prevent unexpected cell usage by GV for outgoing calls.
I used Hangouts to avoid using my cell number prior to Google Voice adding the prefer WiFi and data option when traveling internationally.