Look for Z coded seats. Generally on Latin American flights with regular FC (not BF) configuration, the codes are C for revenue FC seats and Z for those that are upgradeable. I myself am waiting until midnight tonight to grab elite upgrades on the EWR-SJO nonstop for Thursday and the codes as of a few minutes ago read C6...Z6. It looks good for me right now. The Z seats are also upgradeable with 15K miles in each direction without the 30 day in advance restriction.