My best guess would be that it would be a 5-10 minute cab ride depending on time of day and traffic. It really is not far but there is a lot of construction right now on the road that the bridge over the river coming from the Hyatt flows into. (this main street actually has the IC on it.) It is indeed walkable and I have walked it many times (from the trade show not the Hyatt) but IMHO it's a pain especially if the weather is cold/rainy/snowy like it was this past week. During the summer months I would say it would be a pleasant 15 minute walk for someone that is reasonably fit.

According to Mapquest.de it is 3.1 km between the two actual hotels. I couldn't get Mapquest.com to do it so I went to the German site since I speak german. You can probably figure it out even if you don't speak German and it will show you the travel route. Travel time is listed as 6 minutes.