Hi Ernie; welcome.
I don't know exactly which type of terrain can be found in Costa Rica, but what you described should not be a concern with a stock RAV4. But without a LO range, the RAV4 don't like long and steep hills... particularly when the vehicle is loaded.
I don't know exactly which type of terrain can be found in Costa Rica, but what you described should not be a concern with a stock RAV4. But without a LO range, the RAV4 don't like long and steep hills... particularly when the vehicle is loaded.