Foreign pilots are unwelcome in Guatemala as well as most Central American countries and Mexico-- the laws make it so. The exception is Belize, where carriers like Tropic Air and Maya-Island Air frecuently hire foreign pilots when the local talent is not available (both of these carriers use Cessna Caravans). There are also a few smaller charter operators at the downtown airstrip in Belize City (not the International airport you will probably fly into). I don't know what competitive qualifications are or what time of the year your chances are at their best, however, consider doing a "search" on this forum using the word "Belize" . . . . much has been written in the past including by pilots who have worked there or who currently work there.
Good luck.