the Technische Universität in Darmstadt (a town south of Frankfurt) is very well respected within Germany, at least in technical fields. I can't say much about Goethe since I really have not heard anything about it (though that might not be a very good sign). They started teaching Physics in 2008, so I guess it won't be very recognised yet.
Do you speak German? Most Bachelor education is taught in German, and as far as I know physics is. Some more info about Physics in the TU: http://www.tu-darmstadt.de/studieren/abschluesse/bachelor/physik-bsc.de.jsp
Darmstadt is less than 30 mins away by train from Frankfurt, and there is quite a large student community here thanks to the TU. You definitely won't get the big city feeling, but Frankfurt is next door so all its possilibities are open. You will have a student ticket for the train so it won't cost you a cent!
Hope that helps!