Travel to Ljubljana
By carSlovenia has great highways. You'll need to buy an electronic vignette before entering Slovenia. This is new in 2022 - no more stickers on you wind shield, you just enter your car's registration plate. You can buy one on line or at the gass stations near (but before) Slovenian border.
There is a big and cheap parking next to Festivalna dvorana.
By planeLand in Ljubljana (LJU), Trieste/Italy (TRS, 1 hour drive), Zagreb/Croatia (ZAG, 1 hour drive), Venezia/Italy (VCE / TRS, 2.5 hrs drive). We really do use Trieste, Zagreb and Venice airports.
Use GoOpti shuttles from any airport to Ljubljana.