Facetiming while in England?

My whole family has Iphones (4 and 4s) and my mother and I will be visiting England for a week in June and we were trying to find a way to communicate without getting hit with high roaming charges. Face times seems to be the answer because it uses Wi-Fi (the hotel we're staying at has free Wi-Fi) which would mean we could talk/see each other for free since no minutes will be used. However, since they are American phones, will we be able to connect to an international Wi-Fi area, and if we can connect will we simply be able to click the face time option in the contacts and be connected? Or do we need our phone unlocked/jail broken like I keep seeing on these message boards?

When I was living in London the only thing that really worked well for me was Skype on a computer. Not sure if facetime is going to get charged… You may want to contact your carrier and ask them.