I am not sure if this has been put on the forum previously,
but I found Imessage great while in Bali at Xmas.
My daughter had her Iphone set to her email acc and as my partner had roaming I took my Iphone (no roaming turned on)just for using Wi-Fi,the great thing was we were able to SMS each other at no cost as my phone just picked up the wi-fi.
I will use this for all traveling in the future.