Originally Posted by INsano

Um...my uncle was just in Mexico last month with his hero, had the network disabled so he wouldn't get reamed by Sprint's roaming/international charges, and used Skype just fine to call over WiFi. Pretty sure everywhere in EU should be GSM(incompatible with your hero), but I'd make sure the phone "network" is off so it won't even try to find a phone signal.
As to the poster above who said Google Voice isn't VOIP...LMGTFY:

Let me google that for you

It's one of the defining points of Google Voice...to not use the cell networks, so you don't use your minutes...which is a threat to the whole current price structure of...nevermind. But if you don't know what you're talking about, don't post and confuse people.