Naturally it is. In fact, in the next few years the country threatens to succeed the Czech Republic as the most popular central European destination amongst backpackers and independent travellers.
For all that, getting to Croatia isn't as straightforward as it could be. Travellers with railpasses can find train connections to Zagreb on the mainline that connects the Croatian capital to Budapest, several hours to the north, and to Ljubljana (and eventually Venice Santa Lucia) to the west.
Otherwise it's pretty much a question of finding a coach in Vienna or, alternatively, taking the ferry from Ancona or Bari in Italy to any of Croatia's three principal Dalmatian ports: Zadar, Split and Dubrovnik.