I enjoyed this movie and parts did make me laugh. Jerry Lewis is certainly an acquired taste however. When the movie started, I was worried and thought I would abhor the rest. It opens with a ridiculously over acted and unfunny scene where acts devastated to spot the girl with another guy. It was more cringe inducing than funny. This kind of slapstick might have caused a few laughs back in the 60s but it's almost unbearable to watch now.
That being said, there were parts in the movie I did find funny, as silly as they might have been. The bit with the method acting with the girl slapping him. The man and the hat. George raft. The butterflies flying out. Also, I do love the setting!
To summarise, humour is sometimes a bit forced, slightly outdated but still has its moments and charm.