It's easy to find articles about there being a swine flu outbreak in Mexico, but is it safe to go on a cruise that calls at a Mexican port? So far the US government still isn't exactly saying it's unsafe.
Finding their actual advice can prove challenging among the array of government websites and their medical definitions of swine influenza. So you don't have to, here are the two pages updated constantly with the advice from the US government about travel to Mexico with respect to the swine flu. There is also one from the World Health Organization with specifics of where in Mexico the cases are occurring:
CDC - Centers for Disease Control
US State Department
WHO - World Health Organization
You'll note at this point at least, the outbreaks are not near the popular ports of call. Officially the US government is "recommending" Americans "avoid all nonessential travel" to Mexico, but they aren't exactly saying "don't go."
As of Monday evening, the cruise lines are considering what their course of action will be.
Updated: April 27, 8:44pm