I wanted to report how things went. We found the bus schedule for the main bus station, which was next door to the train station we had arrived in, and the departure time to Ljubljana. We rolled our luggage from our nice little hotel, bought our tickets and climbed aboard. In about 90 minutes we arrived. The bus had plenty of room and it was a direct bus, no stops to worry about.
Our only issue was that we had about 30 minutes to buy our tickets and find the bus. We were third in line at the only open ticker window behind a young man and woman who spent a good 15 minutes at the window. I'm not sure what the heck was going on, but the line behind me grew and we all tried to make eye contact with the ticket seller. With 15 minutes to go, I even allowed another traveler to cut ahead of me because she claimed HER bus was leaving in 5 minutes. Finally the couple was moved to the side and we were all allowed to buy our tickets. When boarding the bus, I passed the person I allowed ahead of me. She fibbed a bit on her departure time--we were on the same bus! No harm, no foul. We were all happily on our way to Ljubljana.