We did a tour of Slovenia and Croatia in 2014. We flew into Venice and visited there for several days before heading to Ljubljana. I too researched the bus/train option from Vienna or Salzburg but decided it added unnecessary time and effort so Venice worked out well. We used a Shared Van service from Venice to Ljubljana...6-8 passengers and took 2 to 2 ½ hrs to Ljubljana.....very easy and cost effective. We used GoOpti.

Ljubljana is a lovely walkable city and we found Slovenians to be very friendly, outgoing and curious . Highly recommend! On Fridays in the summer they have a Food Fest in the square.