Signed up for April 2020 tour. After reading all the post about things to do around Slovenia; I want to ask the forum how many days to arrive before the tour starts and what are the highlights to see. Looks like the caves and Lake Bled Gorge are a must but any other suggestions of things to do. RS tour takes us to Lake Bled and through the Alps.
You could fly into Zagreb to start. Spend a few days, then take the train to Ljubljana. Rent a car, drive to Skofja Loka, a lovely small town. Take the scenic drive from there to Bled via the mountains - a beautiful drive via Jamnik and Kropa. Head over to Lake Bled and hike Vintgar Gorge. Drive to Lake Bohinj and check it out. Drive back to Ljubljana, return the car, and meet the tour. (Spread all of this out over as many days as you like.)
I leave for Slovenia tomorrow! Will spend 24 nights there and still not cover the entire country. Trip report coming in late September.
If you're going to Skocjan caves, 20km away in Lipica are the Lipizzaner farms where the horses are raised and trained. They offer tours and you can (pay to) watch a ring practice. Check hours, tours and practice are not daily. You can also just wander around the grounds and watch the horses. It's a peaceful way to spend a few hours.