Yup, definitely best to get to know people before you do such business. I don't know about Croatia but the police in Bulgaria seem to be backing off a bit the last few years, you can smell it somewhere most days in the big central park. But you must be careful. The most likely way to trouble is from scuttlebutt on the streets. And bad suburbs like Levski in Sofia.

One plus with the old communist architecture is those giant parks, it is easy to be hidden. Technically in BG it is illegal to drink there. But the police pretty much don't bother unless you also are causing shit.

Going into building sites is a very bad idea. Security because of gypsies is pretty effective. They will hand you over to the cops happily.

When I was in prison I met one guy who didn't even have any weed and the charge said zero grams. IDK if it was true but you can't calculate why a balkans cop might decide to give you problems. Best to avoid them. But it isn't much more dangerous than Australia for example.