Going to St. Petersburg not finding my usual warnings/scam site

I've had a pause in my travels for a few years and Lonely Planet's scams and warnings section seems to have disappeared. After some googling (finding the usual stuff to look out for) I still feel that I'd be better off asking for some pointers here.

I'll go my boat from Stockholm and I plan to stay in the city for a few days. Is it OK to visit a disco or a bar to talk to people? How's the general English level? If a woman talks to me and is friendly, should I expect to get a price tag shortly?

Anything would be of use. Googling for "travel russia st petersburg" brings way too broad variety.