Speaking another language can be a long, hard road full of embarrassing cultural misunderstandings: being too informal, calling someone’s father a vegetable, saying you have 23 buttholes, ect. Usually, humor is supposed to be the true mark of fluency; if you can understand/make jokes, you have mastered intricacies of the language. That last hurdle is a difficult one to make.
However, this one is humor for beginners-
The sign says “NO TRESPASSING”.
“SON!” (in Spanish) means “They Are!”
Small acts of hooliganism transcend culture/language.