@Supercrypt: Anyone in the world can register them. We have hand selected 5 TLD's to support. As you might notice .edu.gt, .gov.gt and a couple others are "not" available. Those are the TLD's that del Valle won't allow international users to register.
So in short, the 5 available on our site are totally available to anyone world wide for registration
@1Referee: The prices can be found on the link provided, they depend on the TLD really. On that same link provided you can check for availability of any domain with those TLD's.