There are hardly any places that take credit/debit cards and this is true throughout most of Germany. I have only been able to use mine at very large department/grocery stores. There are not many ATM's either (Geldautomats), only inside/outiside banks. So stock up on euro or you'll be searching and searching for an atm's especially in the middle of walking cities like Tubingen. They are only on the edges on main streets.
Tubingen is in the Swabian (pronounced "schway bee an") region of Germany. There is even a Swabian dialect that is quite different from traditional German. Swabian food also has specific characteristics. One of the classic dishes is a spaetzle. Made with a fresh curly pasta and loads of butter, garlic and cheese this comes out of the oven and is topped with sweet grilled onions; kind of a super fancy mac and cheese! I think it should not be too hard to replicate this dish here at home. In fact, a quickie web search found this website with a variety of spaetzle recipes: Spaetzel recipes