A little late to be reviewing, but I only recently had an opportunity to see this movie. I found to be quite hilarious.
It starts off very poorly. The humor is uncreative, blatant, and somewhat gaudy. However, the beginning is largely used to set up the context for which the rest of the events occur. The plot is fairly bland, and although I won't give it away I'm sure you'll see the general direction it is heading very shortly into the movie. That doesn't matter. Plot is only a means to shovel comedy into your mouth. There are a fair share of bad jokes through the rest of the movie, but Cloudy with a Chance for Meatballs shouldn't be judged on the amount of bad humor contained within, but rather judge by what is good.
A simple outline. The movie begins with cheese, bland, and predictable, moves on to ridiculous, then to horrifying, and finally some combination of horrifyingly ridiculous and ridiculously horrifying. There is some subtle verbal humor, but often the best jokes are absurdist.
Allow me to describe one scene for you. A naked man in a giant roasted chicken stroking your head telling you it's going to be ok.