How can the Mainz Hyatt be reached?

I've often stayed in the Hiltons in Mainz and want to try the Hyatt now. I was upgraded regulary into suites in the Hiltons so I wonder what I can expect a similiar excellent treatment as Hyatt Diamond? I would like to check out the Hyatt as the company rate is quite cheaper for my arrival date (end of April). The Hiltons seamed to be quite full during that time.

Did anybody try the restaurant? How does it taste. I'm not looking for food like burgers or spare ribs? The Graugans at the Hyatt Cologne is excellent but a collegue has warned me that the food and wines in Mainz were not as he had expected???