I will need a sim card as soon as I land at Krakow Airport. I need to call UBER to get to my hotel. The alternative is to wait 3 hours for the bus.
Is it possible to get a sim card at the airport?
You can buy a SIM card at any newsagent's including those at the airport but you will need to register it (new law as of July 2016) otherwise it will remain inactive. Each mobile operator has different rules where it can be done. Some can only be registered in the operator's own stores, some have made arrangements for it to be possible in post offices, RUCH newsagent shops, Media Markt and Saturn electronics stores etc. Here is, for example, Plus:
http://www.plus.pl/registration
You can google the other major operators Orange, Play, T-Mobile, Heyah
Which hotel is it that it requires a 3-hour wait for a bus? The train to central Kraków takes less than 20 minutes.
If you don't want to take the train, you can get a taxi right at the airport. When I was there in 2013, they had fixed rates to various zones. I don't remember exactly, but I think it was the equivalent of 25 or 30 USD to my central Krakow hotel. It was a pretty fancy new car, too.