There has been some conflicting information floating around about tax situations for a retiree overseas.
I found a wonderfully clear introduction to the situation written by a Roger B. Adams, EA, here:
UNDERSTANDING TAX TREATIES
I have tried to read these treaties myself, so this was a marvelous discovery.
One of the less-defined situations is retiring and becoming a tax resident of a country without a tax treaty with the US (case in point, Colombia; tax treaty being negotiated now). As it happens in this case, Colombia won't tax retirement funds from outside until they are more than $10,000/month, so you pay income tax in the US for withdrawing from your IRA, but not in Colombia, so no problem. And, it seems that if you don't earn your $ in-country, most places in Latin America won't even pay attention to you (although, I would never recommend an extra-legal situation), except that you may need to show a monthly income to legally stay in-country.
It is not as bad as I thought it would be.
Now all I have to worry about is kidnappings and robberies.