Useful Information
Language
As one of the top student cities and the top tourist destination, English is fairly widely-spoken in Krakow compared to most other areas of Poland. Tourist establishments, including most reasonably sized restaurants and bars will have somebody on the staff who can talk something that sounds like English. Outside of the tourist centre you are likely to find more trouble if you don't speak Polish. You are never far from an English speaker however, and most are more than willing to help translate. German and Russian may be worth a try as a last resort.
Shop opening
Shops in the old town in Krakow (on the streets that radiate out from the market square open late and close even later. The proper shops, which are mostly located just the west of the old town are open from about 9 or 10am to around 6 at night. Sunday sees less shops open than weekdays, though you are unlikely to find yourself stuck for essentials