To the frog
That's the route on which I took my first trail running steps. I used it as my go-to when training for my first 60km trail race. Nice forest route, going up and down all the time. You'll meet someone here and there, but most of the time you'll be able to enjoy the forest's peace.
You can park for free at the trailhead. You can also get there by bus for Vrhnika #47 from the main bus station in Ljubljana.