I would recommend Monchengladbach Friendly to anyone available a great stadium to visit and a very passionate fanbase. I would recommend staying in Cologne to anyone attending there isn't a great deal in Monchengladbach. The Belgisch Viertel is great for bars etc in Cologne and of course you have the area near the Cathedral. Dusseldorf is also another place to stay a bit for more upscale reputation in Germany but a lot of nice bars also and where many will fly back from. Any other recommendations needed let me know.
Yes, totally, I love going to this part of Germany. And to be honest, Cologne, Düsseldorf, Mönchengladbach, Leverkusen etc may as well be one giant city, such are the transport links. Pick anywhere in that conurbation that tickles your fancy.
I really like Düsseldorf, especially Uerige Alt Bier. Cologne is nice too, as is Kölsch beer. I'm from Lincoln originally though so Cologne's cathedral doesn't really impress me
