When we visit Krakow we would like to do the Auschwitz tour and the salt mine tour on the same day, this however ends at 2000. There are no trains that late back to Katowice and we have a 0600 plane to catch the next morning. Any suggestions on getting back to Katowice or should we skip the salt mines?
Your time constraints limit what you can see. I have been there and know the feeling. You might investigate hiring a taxi. I have read about travelers who negotiate with a driver for a special trip. Maybe two drivers or more.
Depends on your interest, but I would skip the salt mine. I have visited two and find them boring.
When you see one room down there you have seen them all, but still you have to tour another hour or more with the group.
You will find Auschwitz well worth two or three hours. Especially if this is your first prison camp. Reading descriptions on the exhibits takes time but I find them fascinating.