We are hoping to see a bit of Greece and then head up towards Croatiawe'd like to see some of the country(ies) along the way but have heard there are some issues with renting a car and driving through some parts...is this true? Can we rent from Greece and drop off a car in, say, Split Croatia?
It's not like No. America where the large int'l. car rental agencies have drop-off offices everywhere. They are independent rental companies regardless of the name (Budget, Hertz, etc.). Of course there might be an exception but I doubt it. It's very unlikely that you can rent a car in Greece and drop it off in another country.
Some of your issues are an EU country to Non-EU country plus a country or two between are somewhat "sketchy" in regards to security or rather insurance risk. Overall, probably little chance of finding a rental company willing to allow it.
thank you all for your advice! you confirmed my suspicions, and clarified my questions.....