We've decided to base in Lake Bled for 2-3 nights and take the local bus into Llubjana for a day excursion. is there a local bus or excursion trip that would take us over the Vršič Pass through the "Julian Alps Loop" and down into the Soca Valley?? I'd prefer to have the chance to stop at a few sights along the way rather than just drive in acontinuous loop. I think the bus could start in either Lake Bled or Llubjana.
There are companies offering guided day tours of the Soca Valley starting from both Bled and Ljubljana, which is your best option apart from renting a car. There are no public transportation options that would allow for an easy hop-on hop-off experience. There are buses running over Vrsic Pass every two hours in July and August, once daily the rest of the year (outside of winter, when the pass is closed for traffic), but they're quite cumbersome for sightseeing.
Some examples of guided day tours:
We rented a car for a day/night to do this drive and it was fantastic! We left from Lake Bled, drove over Vrsic Pass, down into the Soca Valley, and had lunch in Bovec. From there we went to Kobarid where we stayed the night. The next morning we drove to Ljubljana and dropped the car off, since that was our next destination.
If you don't want to deal with the drive over the pass (and the 50ish hairpin turns!) then an excursion trip might be more your speed.
Elaine, I don't see you having the time. If you take a tour or similar they seem to be all day affairs. Even with a rental car it is a long journey there and back. If only staying 2-3 nights total in lake Bled and already planning a day trip Llubjana you have no full day to spare for seeing the Soca Valley.
I thought about it as a side part of day trip myself hoping it could work in an afternoon or morning from Bled with our rental car but seems like it is a 2 hour drive without any stops each way.
Adding in stops and making it a round trip and that will take up a day.
I have seen Tours offering guided trips with nice stops along the way and they have great reviews but leave early morning and get back at night.
Save some time for the Lake or visit closer Vintgar Gorge instead.