I've been to Prague, Bratislava, Budapest, Slovenia and Croatia. I loved Bratislava, Slovenia is AMAZING and Croatia is beautiful but rather unfunnily expensive. Think London. Central London.
And I've been vegetarian in all of them! Prague was probably the crappiest, but I went ages ago in 2001 and I think they will be better now. In Budapest I only ate one "local" meal which was fried cheese on top of fried rice with three fried mushrooms and it was so greasy I didn't want to eat for several days after. But there are Italians almost everywhere and in Budapest I ate at the Hari Krishna restaurant- vegetarian AND dirt cheap! Slovenia is great because it mixes influences from all the countries around it (because its wee) and it has lovely food and AMAZING ice-cream.
Global interrail pass is probably your best bet because the fares really add up otherwise (although you can always use coaches not trains which are a lot cheaper). It covers the following:
Austria, Belgium, Bosnia-Herzegovina, Bulgaria, Croatia, the Czech Republic, Denmark, Finland, France, Germany, Great Britain, Greece, Hungary, Ireland, Italy, Luxembourg, FYR Macedonia, Montenegro, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland and Turkey.
Won't take you to Chernobyl though. I *really really really* want to go to Chernobyl.