I have around 2 weeks (flexible) with a friend to travel in mid September, and we would like to visit Slovenia, Croatia, and Budapest. Though we really want to visit Budapest, the main reason for ending our trip there is the cheap flights between Hungary and the US. We've sketched out the following itinerary and wanted feedback on whether or not it is too ambitious. We are looking for a decent pace of travel that's not too frenetic.
4 days - Ljubljana (with two day trips: Bled and somewhere else)
3 days - Istria - 3 days
3 days - Croatian islands (choosing between Rab, Cres, Losinj, Krk, or Pag)
2 days - Zagreb (is it possible to visit Pilvitce on the bus/train route from Istria to Zagreb?)
3 days - Budapest (via night train?)
We will not have our own car so will rely on buses and trains. What do you think of this itinerary?