[novaCJ]

Colombia (in the cities, at least. Rural areas are still dangerous) is quickly improving under the radar, and is on my short list of Latin American places to visit. I have heard good things about Costa Rica. San Jose (and surrounding towns) are in the mountains and cooler, but still fairly close to both coasts. I would recommend Chile, but I see it's not quite the climate you are looking for. On the other hand, Panama City may be a bit too humid for you, if SE Asia is past your threshold.
Venezuela = Stay away. At the moment, the political situation is a bit unstable, to say the least. Not to mention the incredibly high (unsolved) murder rate in Caracas...
A friend of the family (from Rio) is moving back to Brazil. After speaking to him, he echoed everyone else's comments about avoiding the North and being cautious about cost of living; a refrigerator (for example) costs three times as much there.
Having never been to the region myself though, my strongest piece of advice is to be sure to visit before deciding on anything, you could hate a place you thought you'd love, or vice-versa.