I agree with Gar, language is not a major problem and even in villages locals will have someone who at least has a few words of english!
Be warned that you'll have to bus it to Dubrovnik, as it's not on a rail line. If you're in the area (ex-Yugo) must sees are: Zagreb (the architecture is great, people lovely and it's got good sights), Split (again sights but a day and you're done), Sarajevo (just for the recent history is reason enough), Belgrade (sights, people, culture, sights - great place), Nis (on the Bulgarian border, great sights and real soul). Sofia is okay to pass through, same with Bucharest. But around Edirne and Istanbul in Turkey is lovely. And if you feel adventurous, head deep south in Turkey to the coast - go to what American generals and Georg Bush were calling "Alexandretta" just before the attack on Iraq - and trace the massive city walls.