/ How Safe Are the Polish Cities?
I don't see why you are fighting over statistics. It has little to do with street safety.
The quoted article must be old - it's been 17 years of democracy now, mafia has been handled (at least the 'civilian' divisions, I don't know about industrial/political influence). The police has increased in numbers, a new generation of officers has been recruited. If there are no wardens walking or driving around, they are likely to come quicly once alarmed by phone. There are some general rules to follow though.
My opinion? Stick to the west half of the country, preferably cities. Stick to the city centres where there are some foreigners, excluding railway stations, where homeless go. Stay away from outskirts and concrete jungle as well as places known for hostility towards foreigners (e.g. notorious Nowa Huta or Lodz). Say hello to your neighbours so that you're seen as one of them, not the 'stranger'.
About wrong times and wrong places? Avoid anyone who may have been drinking (in all humans alcohol increases agression, nevermind the nationality). Careful at weekend nights and stay away from football fans (no hair, scarves, singing loud) and army recruits (no hair, triangular painted 'coats', singing loud). Avoid those who spend their time hanging around doorways, parks ect. Move around quickly and proud, sneaking through places only makes you look like a potential victim. If in doubt, run towards people - with witnesses you are less likely to get mugged.
About thefts? Just be reasonable - don't show off with your mobile, don't carry too much cash or documents with you, watch pockets in lose clothing (e.g. jacket) and back trouser pockets. I have lived in Poland for years and haven't been mugged or robbed once.
Play it safe.