Is that salary enough to spend a decent life in Krakow with little saving..?
Yes! You should be able to rent a small 1 bedroom for between 1300 - 1600 zloty close to the center. I used to pay 2000 zloty for a slightly larger one bedroom but it was also only a 2 minute walk from the Rynek. Plus extra costs you may be looking at 2000 altogether.
That leaves you with 4k left which is plenty even for Krakow.
I'll be moving to Krakow early next year. I would like to know if 20,000PLN gross salary is good enough for a decent living in Krakow?
I am not sure if this is a serious question or not........!?