The Facebook page for Percy Jackson: Sea of Monsters released the official dates for PJ2! According to the dates Mexico will get to see it first on August 9th, 2013, a whole week before the US gets to see it on August 16th, 2013.
Here are some of the dates
For the full list, go to their Facebook page or view the picture below.
UPDATE: The release date was changed to August 7th, 2013. Read more here.