Ok, I know the picture isn't great, but that is what you can expect from my mobile camera.
Anyway, the green sign (almost illegible) says:
يمنع منعاً باتاً إلقاء القمامة تحت طائلة المسؤولية ودفع غرامة مالية
I had the idea of taking this picture (which I will replace with a better one if I can) when I saw a girl walking gracefully across the street to throw their home trash under this sign... Too bad.
The sign literally reads in English: "It is absolutely forbidden to throw trash here, responsibles will be fined"
This is a daily scene by the way, and not a solitary incident.