I would come into Slovakia via the Dukla pass . Slovakia is nice in the North - east around Bardejov and Kosice . Presov is pretty industrial but is surrounded by mountains . there is a large castle (ruined) at Spisky Hrad south of Presov . i wouldnt bother heading south as there isnt much to see unless you are going near Budapest and the Danube . If you have that much time then Eger in Hungary is worth a look -effectively head south from Bardejov . It will be extremely hot during June , July and August - in the mid 40 s .
Fuel costs about the same as the UK but engine oil for bikes is well expensive . Room costs are preety cheap as is the food and
. Watch out for radar traps they are everywhere and very very sneaky eg in bushes in the middle of a field .
As for motorways there are some that are near the tatras / polish border but they are mostly unfinished and stop abrubtly .
Would be interested in your ride through that bit of poland as travelling thru there next year to visit a friend in the Baltics