In reply to Solsbury:
Recently been to Slovenia, with the aim to head into the Julian alps but only to encounter some pretty horrible rain hence called off the activity for a cultural experience.
First of all wild camping is against the law in the national park but there are plenty of camp sites around. Bled, is very busy especially at that time, and as someone's already mentioned, Bohinj will be a much better choice. Couldn't remember where exactly the campsite was but google will tell you for sure, if not, arrive, and ask around. There are also plenty of huts there in the mountains so a hut walk should be fairly do-able. The alps is big enough you can easily "get lost" in it for a couple of days, if you're up for the challenge you can even consider crossing from Kobarid towards Bohinj, that's a fairly long walk and takes in a fair few of the bigger summits, route finding is important according to locals unless you want to end up on practically a climb (solo), if you're lucky (or not) you might even get to see remnants from the war littered around in the deeper parts. Either way you've hit probably the best time to do Triglav.
Climbing wise there are a few crags up north and certainly some mountain routes to be explored, if not, the most popular spot would be down south closer to Italy, a place called Osp, which is close to the town Koper. Generally sport climbing for all levels and Koper is a good getaway, if you fancy something more touristic, From Koper you can get to Piran, where you can rent a bike and cycle down the coastline in the direction of Croatia, where you will see the salt pans, that time of the year I'd presume they'll be making salt in the traditional way. Further into croatia you can also enter the salt pans but not been that way so don't know what's on the other end. The sunset from the top of town at the old castle in Piran is also stunning.
On a different note, don't forget to try a Potica, which is a walnut cake thingy, very tasty, I'm trying to make my own now! And Pleskavica, cevapcici, and of course, drink plenty of slivovic or rakija! Local beer isn't too bad but compared to Niksico from Montenegro or Peja beer from Kosovo, it's a bit behind.
Hope the two cents helps!