I would live in Costa Rica

Unfortunately you must be a permanent resident or have a work visa to work here. As far as I am aware, all those practicing in medical  professions must be re-certified here in Costa Rica with exams in Spanish, and you would be required to be bilingual.

Check out this thread:
Immigration

Were you employed in New Zealand and Australia as a nurse? If so, did you require a work visa?

While I agree that many foreigners do work 'under the table' but in the medical profession, I do not honestly think that someone would be employed that didn't speak Spanish nor had the required, legal paperwork...at least I would hope not.

English speaking patients  are a very small percentage of even the top hospitals. A few years ago, we spoke with local nurses at the Hospital La Católica and asked if they would get paid more if they had good English skills and they said 'no', they  would receive no addional benefits nor were they encouraged to learn/practice  English Doctors, yes, and since they take many courses in countries around the world, they are [i]usually bilingual.

Encourage them to visit and ask round, rather than give them the wrong information.

Kohlerias, who are you addressing this to? I only referred them to another thread about immigration, that is here on this forum. I have no idea whether all the info on that thread is correct or not. But I don't recall saying anyone should immigrate here to be a nurse without proper credentials.

Sorry, I should have mentioned that the post I disagreed with, was the last post on the thread you referred to in response to the OP louisonpons

Article that I suggest you read, louisonpons so that you don't find yourself in a position you may regret.

... who's on first?   

No, Who's on 2nd!