We will be renting a car in Dubrovnik and driving to Split and Plitvice Lakes and then plan to drive around Slovenia. We will stay in Ljubljana and somewhere in the Julian Alps. Are there any restrictions on taking the car into Slovenia?
You’ll need to check with your rental car company, it really depends on them.
We rent often in Croatia and drive to Slovenia. Just tell the rental agency. There is an extra charge, I believe we paid about an extra $100.
We rented in Bratislava through Europcar. No issues moving through Slovakia, Hungary, Croatia, and Slovenia. Just make sure your car is equipped with a vignette, usually for the issuing country. You need one for Hungary, and Slovenia. The vignette tracks your car's license plate. In Croatia, you have to pay tolls at toll booths.