Best options for using iphone 4 oversees?

First of all, I need to keep this as cheap as possible. Im traveling around the world for 8 months, and am on a very low budget. I know there are many options for doing this. One that Ive heard of is putting the phone in airplane mode then turning on wifi, and using it that way. I know I cant receive or send calls or texts, but would this allow me to send emails? I would like to be able to call my family, but if the airplane mode is the cheapest way to use my iphone oversees then I can just send out emails. If anyone has done this before or knows the cheapest way to let my use my phone please help. thanks