Dear sir, you can travel with your passport from the United States and do not require a visa, because you are still a Costa Rican citizen. It is important that you travel with your valid ID. If you do not have it, when you are there you can process it. In the Civil Registry they can be given the same day.
No but they have to Pay taxes
The truth is that I think not, but I am Cuban American and I am 15 years old. I'm not going to that country. Sorry I'm not very helpful.
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