We went to Dubrovnik and the Plitvice national park. Dubrovnik was stupidly hot (for someone living in Newcastle) 35+C. The national park was pleasantly warm in the high 20’s.
Its a big country so you could be in the wrong place. We spent some time with these people but our ride was fire road and tarmac.
I think you may struggle. When we were there it was noticeably still scarred by the war. We were in a bit that was fought over quite heavily to the extent where you weren’t allowed off some roads as there were minefields marked and unmarked in the fields.
I would guess that up in the north would be your best bet. Maybe even over the boarder into Slovenia.