Let's be very clear about this: if you are offended by bodily-function jokes, crude sexual innuendo, or Idiot Humor in general, do not watch Bean. If, on the other hand, you think blowing one's nose can be funny....
If you've never seen Rowan Atkinson's Mr. Bean, on PBS in the U.S. or elsewhere, it may help to know that Bean is the sole inhabitant of a very strange world. His encounters with the world of normal human beings form the basis of his TV shows and this movie. Bean wreaks havoc everywhere he goes; this time, he's in California, and the painting Whistler's Mother is involved. That's probably all you really need to know in advance.
I've seen quite a few of the Mr. Bean television shows, and for the most part I don't care for them. This is worth noting because for almost every gag in this movie I knew just what to expect. I could see the set-up coming a mile away, I knew it was going to be something stupid and/or juvenile, and I still laughed my ass off.