You can register to your home country. The only downside is that you might have to pay a charge for delivery of the books you will purchase. I know Canada has a 2$ charge per book. What some people do is register their Kindle with US address and buy Amazon.com gift cards to pay for the books. That way you save the 2$ charge and you can use your credit card (to pay for gift cards). I'm not sure if this is still valid but when you do buy it from Amazon.com, mark to send it as gift. That way when they ship your Kindle it will not be registered, allowing you to register it once you receive it. Worse case though, you can unregister it and re-register under different account (if you decide to register to your country). Bottom line is, no matter what you will be able to us the 3G in your home country.
Take a look at this
blog entry, it can be useful.