The S2, as my right honourable Hamburg Blue identifies is a way to the ground. An alternative S-Bahn route is the S1 destination Wedel will take you to station Othemarschen, here also you can get a free transfer to the ground. Be prepared to be frisked on entry to the ground. I was there for a German international match and a Hamburg Vs CSKA Moscow Chumps league game and both occasions I was frisked.
Accomodation location - I would recommend Altona. Here you are in a prime location for one of Hamburgs larger S Bahn and national rail stations that can take you without change to Central Hamburg, Reeperbahn, Airport, AOL Stadium and links to other major German cities.
Altona is teeming with superb sports bars and good value eateries.
If you want an Irish bar, the main one is Finnegans Wake in the centre of Hamburg. This is one of the Centres few bars. It is located very close to the Rathaus (Town hall) Jungfernsteig station is the closest. Here you will be welcomed by Eamonn and his crew with traditional irish beverage, food and hospitality.
For a bit of sight seeing, I recommend a boat trip down the Elb, for just a few euros, one of the ferry boats will take you from Tuffelsbrucke (Devils Bridge) located on the bus route out to Blankenese, and will bring you back into the centre at Landungsbrucken. A great way to see Hamburgs heritage.
Nights out - Infamous Reeperbahn has all you want. Try Molly Malones/The Academy or Draft house which are located on the south side of the reeperbahn. The Doll house has some sights to offer too. Just be very wary of pick pockets, and DO NOT WITHDRAW CASH FROM ANY ATMS on that stretch. You have an 80% chance of being mugged.
Just a few pointers for anyone going, if anyone wants any specific info on Hamburg, just ask