It's the writing ...
Just saw this for the first time today after watching "Best Worst Movie" on Netflix.
I have to say, small budget issues aside (and those affect lots of aspects from wardrobe to sound, lighting, etc.) what sent this movie into the "laugh out loud" zone was the HORRIBLE screenwriting. The simple fact that the writer's first language is not English but Italian explains everything. The lines were so stilted and unnatural, even good actors would have been crushed by them. At one point, as the one guy is trying to save his friend who's already half-transformed into a potted plant, he literally says, "Don't fret." No teenage boy in that situation is going to say "Don't fret," but from watching "Best Worst Movie" the Italian director (and obviously the writer, his wife) think they know how American teenagers talk. That conceit is the fatal flaw in this film, not bad acting.
But on the bright side, it's also that makes the film so funny and enjoyable ... but I just wanted to mention it because I think the actors take a little more heat than they deserve, when it truth, it's the screenwriter that ruined any real merit this picture ever had on its side.