Is it true Mexico attacked the US on behalf of the Nazis during WWII?

Not at all.

While Mexico had broken off relationships with the Axis after the attack on Pearl Harbor, they had stopped short of a declaration of war. They were still being wooed by both by Germany and Fascist Spain. Large Italian minorities also exerted pressure on the government. The treaty between Stalin and Hitler had cooled the anti-fascist fervor of the Mexican Communist Party and had indeed made some of them pro-German. Thus the Mexican Government was caught between its own left and right wing partisans and was frozen into inaction.

Now, a miscalculation by Germany provided the impetus to break the stalemate. Numerous submarine attacks on Mexican ships, coupled with a massive propaganda campaign launched by the U.S., British and French began to turn the tide of public opinion. Fearful that an invasion by either Germany or Japan would lead to a massive invasion by the U.S. and turn Mexico into a battleground, the Mexican government, albiet secretly, had permitted U.S. agents to enter the country to train Mexican counter-intelligence forces and to help secure both of Mexico's coasts against possible incursions by saboteurs. There is some evidence that Germany, Italy and Spain did maintain extensive spy networks and had planted saboteurs in the Federal Republic who were planning to take over Acapulco and launch attacks against aircraft factories in San Diego. Prompt action by the joint Mexican-U. S, counterintelligence forces nipped several such plots in the bud. The final straw was the sinking of a Mexican oil tanker, the Potero de Llano and in June 1942 Mexico declared war against the Axis.

Now the leaders of the Mexican military, seeking the glory that can only come to generals from war, began to clamour for an active part in the fighting. Even President Camacho is said to have expressed a desire to lead the Mexican Army into combat, saying that only the Presidency was keeping him from doing so.

However, only the already modernized Mexican Air Force was to actually engage in combat. Mexican pilots received additional training in the United States and in 1945 fought valiantly in the air war in the Phillipines. Only one squadron, Number 201, actually saw combat. Nicknamed "The Aztec Eagles," they flew P-47 Thunderbolt fighters and offered close ground support for U.S. and Philipino ground forces as they struggled to liberate the islands from the Japanese. Decorated by the United States, Mexico and the Phillipines, its 31 pilots and approximately 150 ground support personnel were the only Mexican military force to serve outside of Mexico. Of the squadron's 31 pilots, 5 were killed in action. Its personnel, both pilots and ground support elements certainly deserve to be regarded as heros by both Mexico and the United States.

Also unrecognized, untold numbers of Mexicans, particularly those with relatives in the U.S., flocked across the border and served in all branches of the U.S. military. How many of them were killed is unknown. For those who chose to become U.S. citizens, citizenship was automatic. However, over the years, many returned to Mexico despite their new citizenship.

Although the role of Mexicans in combat was minimal, the denial of Mexico as a safe harbor for German submarines was of great importance. Mexican oil also helped fuel the U.S. war machine. With over 6 million American men in the armed forces and thousands of women in the factories, Mexican agricultural workers kept the food chain moving and, as we have already noted, Mexican raw materials were vital to the war effort. The supply was secure from submarine attacks and did not tie up warships in convoy duty.

Finally, although they depended on U.S. help to do so, the determination of the Mexican Government to resist the forces that might well have created either a Fascist or Communist Government next door to the U.S., removed the threat of sabotage or across-the-border forays that would, in essence, have necessitated either an American invasion of Mexico or the deployment of large forces to guard its southern border. Either one of these alternatives would have seriously hampered America's march to victory.

No it isn't true that they attacked though it is true that Hitler sent people to Mexico and had a plan for Mexico to join Germany attacking the US. The scary thing is that if Hitler didn't attack Russa in the winter and waited for spring we would probably be speaking German along with the rest of the world right now. Mexico did have people on Germany's side and people on the US side. It isn't fair to paint them either way because nothing ever happened and in general we have enjoyed pretty good ties with Mexico. Not great though above average.

Maybe your thinking of WWI and the Zimmermann Telegram.

it was a communication between Germany and Mexico that if the United States entered the war against Germany that they would offer to help Mexico gain back territory lost in the Mexican -American war.

http://en.wikipedia.org/wiki/Zimmermann_Telegram

Not true. Germany sent a telegraph to Mexico during WWI

(Zimmerman telegraph). It said if Mexico allied itslef with Germany then they would get some of their land back if Germany won the war (or something like that youll hav to ask a historian for more details).

Mexico never attacked, but it is absolutely true that the Kaiser went to mexico and tried to get tham involved offering money and to get their land back ( cali, texas ) but they didnt go for it. it was also too late and most of the world new the outcome. it was more of a desperation act...

No, but Germany did try to persuade Mexico to attack America. That was a strong contributing factor that led America into WWII.

No, Hitler did try to form a pact with Mexico in order to pull US troops back to the US to defend the threat of a Mexican invasion but they never signed the pact.

The kaiser sent a letter to Mexico during WWI promising to help them get "their" land back if they helped the Germans. the letter was intercepted by the US.

not true by they did try.

the biggest reason that they didn't was because the Mexican navy had gone home for the day and the Mexican air force couldn't get the plane started.

That's a good question, I was wondering the same thing myself