Motorcycle rentals: Dubrovnik, Vienna, Prague
silverwolf here, from Vienna, Austria.
Will try to answer you questions.
First, see your local AAA for your international drivers license...is simply a translation of your original. Costs about $15 now I imagine. Is sometimes helpful with rentals. sometimes you need that and sometimes you don't. Good to have along however.
Your best bet for rentals would be Vienna. Croatia is beautiful to travel, as is the Czec Republic. Motorcycle Rentals in those two countries are difficult.
Vienna has a good assortment of rental possibilities. As to prices, let's take the 650 cc to 1000cc size motorcycles: they cost from around 110 euros to 140 euros pro day...the weekend packages (Friday afternoon to Monday morning) cost up to 270 euros for the package rental.
There are good day rides out of Vienna...if you have two or three days there are some great rides here in Austria, with jaunts into Slowenia, southern Czechian, eastern Hungry, or northern Italy also. For these you need to be a seasoned rider.
If you happen to choose to ride out of Vienna, perhaps we could ride a bit together. If I can help you with that just drop me an e-mail or post!
greetings from Vienna, silverwolf