I’m sure you can figure out what the sign says…you don’t even need to speak Serbian…pictures (except at McDonalds) are universal. If you guessed Beware of Dog, you’d be right. The sign actually literally says (You) take care about the dog. But the meaning is watch out for the dog. Beware of dog, in other words.
Yes, the Serbs have pets…some have cats, some have dogs, and some have none at all. All in all, a condition that is very similar to the US.