At the upper managerial level, as throughout the rest of Europe, I'd imagine most would know quite fluent English!
Not the bods you deal with when registering a business at the tax office (though in Warsaw they do get a discount for Callan Method lessons if they want - most don't take up the offer), nor the people at the town hall, GUS, ZUS and KRS - I think there's about a 20% chance that they'd have basic conversational English.
Large private companies tend to be a different matter.