I'm not heading the game but if anyone hasn't booked yet I would recommend the Karakoy area to stay in. I've stayed here several times many bars, restaurants round here a local speciality meal is the Fish Kebab! You can walk to the stadium in around 30 mins a long the water there is more here than Taksim square from my experience and Taksim is a bit of a boring place compared to Karakoy. If you have several days in Istanbul I would recommend travelling from the ferry port in Karakoy to the Princes Islands for a day trip or a much easier trip that being across to the Asian side of the city in Kadikoy especially at sunset which is pretty special with the Galata tower and the Mosques in the background. Drinking wise the Asian side is generally cheaper and more authentic experience. Any other questions feel free and enjoy Istanbul if you have a few days it's a city with so much to see.