I was going around to take some pictures of signboards meant for the treasure hunt next Friday, when I saw this interesting sign. It made me laugh in my car. If anyone had seen me then, maybe they'd think that there was laughing gas in the car.
Not exactly in perfect English—perhaps there's still room to improve, grammatically—but I suppose we can more or less get the idea of the warning. A good example of the "Communicative English", i.e. if you can understand it, then the sign has served its purpose.