I'm having a hard time trying to understand why anyone would want a country with bitcoin as the main form of currency. As a really volatile coin, prices would raise and fall almost daily, as globalization made almost every single product international. Living in the island would be a really terrible experience, or just plainly impossible. It would make bitcoin a "real" currency... But that would change nothing on how things work today. It's a bad idea, in general.
Actually the more people are using it the less volatile it becomes. More distribution = more stabilization. If a country started using it as a main currency, there would be 20 million people using it on a daily basis. That's 20 million more users who have to turn their savings into Bitcoin.
We'd have a sharp increase in price, a lot of new users that will receive their wages in Bitcoin, more stability in the market as new people won't be playing, they will be using it to buy stuff, which means they won't be dumping or reacting to dumps, as there will be nothing to dump into with no national fiat currency.