This is not really a horror movie. Sure, there's a lot of blood, limbs and heads fly all over the place, but you never actually get scared. It's really more of a romantic comedy, and quite enjoyable IMO. TWO love stories are happily developing in the middle of the carnage. Lots of laughs, some intended by the producers, some not.
There are a couple of people in this movie who can't act at all, sure. However, they just say a few words and then get eaten, so it's not a big deal.