I hear a lot of people making excuses for this movie based on the low budget. However, the movie fails in terms of acting, writing and direction... all areas that don't necessarily cost a huge amount to get right. I've seen many movies made on even lower budgets that were far more entertaining and well-crafted.
The story is classic horror cliché. Five attractive young people go on a road trip to a secluded Mexican beach. Of course, something is terribly wrong with the beach and they start to die one-by-one. I won't go into the details of the inane plot, but let's just say it has to do with the curse of a cult leader called "El Gringo" (yes, that's actually what he's called) and people being turned into blood-thirsty zombies who hunt by night. So it's basically a bad, zombie b-movie set on a Mexican beach.
The acting is pretty labored and the story gets dumber and dumber as it progresses. There's plenty of gratuitous nudity from the attractive female stars, which was maybe the highlight of the movie. Some movies are bad but don't take themselves too seriously, so they become fun. "Trespassers" seems to take itself way too seriously, and winds up not very scary and not very entertaining.