Costa Rica. If you're going south, Costa Rica is the third oldest democracy in North America and has the 2nd highest literacy rate (after Canada). They have good checks and balances on their democratic system (i.e. term limits). They don't have a military but have a large national police force. They have good programs designed to attract ex-pats. It's really the only choice. All the other central american countries pale in comparison when talking about a stable, safe, democratic nation. Caribbean on one coast and Pacific on the other. A buttload of protected wilderness areas. A city with an ex-pat english speaking population and an english language newspaper.
I don't know what the requirements are now, but 15 years ago if you could prove a $1000US per month pension minimum you could qualify for official foreign pensioner status which grants you all the same entitlements (education, health care etc) as citizens.