<<Disclaimer: Verify this information before applying it to your situation.>>

Thanks to everyone for your replies.  The consensus is there should not
be too big a problem as the Mexican diet is corn-based, e.g. tortillas,
and the like....even corn bread.  The caution is to watch, though, as
there are also the same products made out of wheat.  When we return in
March, I'll let everyone know what works and what does not regarding a
celiac diet in Puerta Vallarta.