United States
"The Department of State alerts US citizens of the health risks of travel to Mexico at this time due to an outbreak of H1N1 “swine flu.” The Centers for Disease Control and Prevention (CDC) has issued a notice recommending that American citizens avoid all nonessential travel to Mexico at this time." Read the complete
US State Department Travel Alert
Canada
"As of April 27 2009, travelers from Canada are recommended to postpone elective or non-essential travel to Mexico until further notice." Read the Travel Health Warning from the government of Canada.
United Kingdom
From the Foreign and Commonwealth Office: "We are now advising against all but essential travel to Mexico."
Australia
The Australian government gives this advice to travelers: "We advise you to reconsider your need to travel to Mexico at this time... If you do decide to travel to Mexico, you should follow the advice of local authorities and monitor the media for updated information about the spread of the influenza virus. If you are in Mexico and concerned for your health, you should consider leaving."


This is not the most updated info. Im just a US citizen looking to spend a vacation in Mexico only if the conditions are not perilous. This is where you can find the most updated and gov relevant info:
http://travel.state.gov/travel/cis_pa_tw/pa/pa_3028.html
Hi, you’re right, this is not the most recent info. If you’ll check the date on this post you’ll see that it’s dated April 28, 2009. You can find information about the most recent travel alert for Mexico here: Mexico travel alerts.