I don't think Chavez's intended audience was Mexico. He's playing to his own people and other potential allies in some South American countries.
I agree with you that Chavez was playing to a domestic audience but I am sure he means war on us. The bitter craziness of his words, and the fact that they are 'just not done' in diplomacy signals creepy aggressive intentions. Since Chavez's lunatic talk, there have been banks bombed in Mexico over free trade. His ambassador who was kicked out was in bed with the bombers. Those bombers are active in the US. I fear that when he says 'war' on free trade, he intends to take it to us and Mexico. Fox better get ready to fight because he might have to. The thug has struck, not just with words but physically too now.
Chavez is intending mexican audience, he has been both attacking Fox and flattering "the mexican people", ALL the latinamericans already know Chavez is Castro's heir and that he has a international agenda (is believed that he sponsors all the socialist parties in Latin America)