I live in San Diego and if it's one thing California is good for providing, it's people who don't signal or look when changing lanes.. so yes, I've tried hitting my horn. Key word, "tried."

Carbon's right, it's about a 40% success rate. but I'm persistent so I just keep punching the wheel until it sounds and by then I've got some innocent bystander's wondering why I'm honking at them.. haha