I spent two weeks in Poland last month, though not in the city you're visiting. we spent a couple of days in Gdansk, a day in Malbourg, and a few days in Warsaw. The rest of the time we were sailing on the northern lakes. We had a great time, and as part of the sailing regatta, attended a number of official functions where many toasts were drank in neat vodka. As already advised, just be careful. The beer is fine, but overdoing it on the vodka is too easy, and before you know what's happened it'll hit you. The Poles are used to it, so don't try to keep up with them.
The history and culture to be experienced are excellent, if you have time apart from the stag do. Despite the formidable devastation of their country and population during WWII, followed by years of communism, The Poles have rebuilt their cities, castles, churches and palaces all to the original appearance. Everywhere there is a sense of optimism and national pride.
I'm going back next month, and probably again later this year. Have a great time, and take time out to see the sights of Wroclaw.
The currency is the Zloty and you'll get about 6 to the pound (4 to the Euro). A beer should cost only 4 or 5 zloty. Food is good, especially the soups which are just excellent - you could live happily only on Polish soup so don't miss them. Most cities have trams, and a 24 hour ticket costs about 7 zloty. tickets are available at the small kiosks which are everywhere, and I imagine it'll be the same in Wroclaw. You will of course need to buy a city map which shows the tram routes, but all the kiosks will sell these.
Good luck.