Alien life forms have spread throughout the U.S.-Mexico border region leading to the quarantine of half of Mexico. The U.S. and Mexican militaries are battling to contain the creatures, with a wall stretching along the American border. The story follows Andrew, an American photojournalist helping his wealthy employer's daughter, Samantha, get back to America. Their journey takes them across Central America and eventually into the 'infected zone'
http://en.wikipedia.org/wiki/Monsters_(2010_film)
Some how I'd never heard of this UK film until a friend of mine told me about it, looks fantastic!
