Been thinking about a trip to Costa Rica myself, and the research Ive done has been mostly on a world sex guide forum (all straight, no ts scene threads). There was a couple of mentions about how to avoid the "trannys" but like you, I can use that info to find them. Check the Jaco thread and San Jose threads for the 2 or 3 mentions of ts.
Thanks for the help. I did check the world sex guide and got the same information about what to avoid. I also found a site www.costaricaticas.com with the same type of information. If I find something useful I will post it.