I would not recomend taking a weapon into Mexico. There laws are allot stricter than ours on this subject. That said, I don't think you should consider a folder for self defense in a central american country where you may be up against a machete. As far as serrations go I would not travel anywhere with them when your gear may be inspected by officials of our country or those of another. New, shiney, tactical looking knives are best left at home or take two because you may be asked to share (ha ha) especialy in forgien countries where bribery is more common than in the good ole US. Pocket worn knives and fixed blade camping tools/utensils are the best bet IMHO. Well used tools don't get near the scrutiny that a brand new FS spydie stamped "military" would for gosh sakes. And if you need a weapon to go there, then don't. Can't you hear your dad telling you stuff like that!
rant over - all the above is of course just the opinion of just one person and please feel fre to disreguard it at any time.
peace,
chet