Just a heads up, Jailbreaking alone will not allow you to switch networks. You need to jailbreak the phone, THEN unlock it. And as of now, you can not unlock the iPhone 5.
Also I may suggest getting the iPhone 4s. It's a global phone, still super powerful even when compared to the iPhone 5, cheaper, and has the traditional 30 pin connector, not this new crappy lightening connector. ie. cheaper accessories, and it will work with anything made for the iPod/iPhone/iPad since 2001
-Wahugg