If you want to hitch hike from Nowy Sącz to Slovakia you should take a bus to PKP railway station towards Piwniczna, get out at Piwniczna stop, then walk a little distance - you will see Biedronka market; many Slovakian come there for shopping so there is a big possibility that you will find someone in front of the market who will be able to take you with his car towards Stara Lubovna; you can go also farther with the street and try to stop cars at the roadside.