Krakow vs Warsaw to Prague?

Would you recommend renting a car and driving from Krakow to Auschwitz, then Auschwitz to Prague and returning the car there?

No, because you'll have a huge drop-off fee if you return a car in another country. I don't even know if a Polish rental place will allow it, although I've never tried it. You don't need a car to get from Krakow to Auschwitz - there is easy public transport and you don't want to have a car within Krakow because it's a large pedestrian zone.

I'd say take public transit (train or bus). The weather (in Poland at least) will likely be somewhat dreary and cold in November (not a great time to go, October is much better). One VERY inexpensive option between Krakow-Prague (called Praga in Polish) is to take Polski bus, but it's a 7 hr 25 min journey (P6 express route).

http://www.polskibus.com/en/timetables.htm

Thank you, Agnes.

The more ai think about it, the more I feel that maybe we will bypass Auschwitz this time and include it with Poland when we go to Germany. What do you think?

Car would be too expensive and it's not needed. The best connection from Krakow to Prague is to take a bus to Ostrava Main Train Station and then by Supercity train. It's the fastest. Or you can take overnight train. Or if you go to Warsaw instead there is a direct train to Prague but it takes quite long. I would fly. There are direct flights from Warsaw to Prague unlike from Krakow from where you have to change planes. I would not bypass Krakow when going to Auschwitz. They are less than hour apart. I would kill two birds with one stone.

Lina7277,
If you literally only have 1 full day for Krakow, then put it off to another trip (getting there is an effort that justifies staying for a longer period). It really deserves at least 2 full days plus another full day for Auschwitz (there is also a very interesting Salt Mine nearby, so that would be another half day or less). I would dedicate at least 3-4 full days to the Krakow area (if you have more, then Zakopane mountains are a great side trip).

Your trip seems very short, so I would stick to Prague and Budapest this time around - those can easily fill up 6-8 days. Heck, I think Rick Steves' tours for those two cities are 8 days at least, and tours are very time-efficient (more so than do-it-yourself trips). If you try to jam in Auschwitz and Krakow plus the time it will take to get there/ get back (they really should be done together because they're so close), then you're going to have a very busy, rushed trip...so better to leave them out and visit at another time.