Still easily the best school in that area of Germany:
http://www.uwid.uni-wuppertal.de/en/start.html
http://www.uwid.uni-wuppertal.de/en/cooperations/international.html
The english site is a bit spartan.
You can drop them a mail and I am sure somebody will be glad to show you around on campus even off-semester.
It is 40 min from Cologne by train or car.
mo-i