Hi! We are spending a few days in Croatia (start in Zagreb, to Plitvice, to Istria), then will head to Ljubljana to see friends. We need to drive to Slovenia due to timing--bus service is limited & we need to be there by a certain time. We want to rent in Zagreb and drop off in Ljubljana but I'm not finding a lot of options with a good price. I want to make sure I don't get a company that's reliable, that doesn't have a bad reputation. The companies being offered up are Sixt (the most economical by far), then Avis, Thrifty, etc. Should I steer clear of Sixt and stick with the major international brands? Any advice would be appreciated...thanks!