Düsseldorf is a small city, in either case you are 3 to 4 €uros away from whatever you want to see
Immermanstrasse goes from the train-station towards the business center, and is full of good japanese restaurants
Median-hafen is the new section, there are a bunch of nice new bars and restaurants, a multi-plex, a starbuck, etc. Like living near the mall
The Alt-stadt and the bars are around 600 meters away (in both cases), so if you can walk it is not a problem
but you might consider trying the Orangerie, which is a boutique hotel right near the river
http://www.hotel-orangerie-mcs.de/