SFX appears to specialize in certain geographic areas. Mexico certainly is one of them. There are others, which are discussed in the exchange forum as well as in Ask SFX. We've got some friends going on a guest cert to Kona Coast 2 in a couple of weeks on a 2BR/2BR exchange which cleared about 11 months out. They seem to have pretty good coverage in Hawaii, on Kauai and the big island, anyway.
Properly shared, sometimes a difficult trade can get the attention of the SFX rep here. Hope it works out for you.
Pat