For lunch try Kopps. It is famous for hamburgers and custard. http://www.kopps.com/ No fancy sit-down place but there are benches outside where you could sit to eat.

We always like Pandl's. http://www.pandls.com/

http://silverspurbbq.com/ We have been wanting to try this restaurant.

We like Rudy's Mexican Restaurant downtown.

I think that Maders and Karl Ratzsch's are over priced and overrated--untless you like heavy German food served in a stodgy atmosphere. And I wouldn't call either one of them casual.
All of the Bartolotta restaurants are quite good.

For Mexican, we like La Perla www.laperlahot.com, La Fuente, or Botanas www.botanasrestaurant.com, all at 5th and National, in the heart of the near South side Hispanic neighborhood.
For Thai, our favorite is Singha Thai in West Allis www.singhathaimilwaukee.com. From your hotel, you could walk to The King and I www.kingandirestaurant.com.
For Indian, try Maharaja maharajarestaurants.com or Mayura mayuramilwaukee.com, both on Farwell on the East side.
Sitting outside on the river at John Hawks pub www.johnhawkspub.com (good salads and burgers) is very pleasant.
In the Third Ward, just south of DT, we like Tulip (Turkish) www.tulipmilwaukee.com and the Palms www.palmsbistrobar.com. Coquette Cafe is also in the Third Ward, and is very good.

Thanks for all your suggestions, sounds like we have some great choices.

I looked at the menus for Maders and Karl Ratzch's and agree they look over priced. I can get good German food where I live but a couple of my friends can't and are interested in going to one of the places.

If you do go to one of the German restaurants, I'd choose Karl Ratzsch's over Maders.

I second the suggestion of Mexican food in the Walker's Point area -- you can't go wrong with La Perla, La Fuente or Botana's.

Love Coquette Cafe, Pizzeria Piccola and Singha Thai.

I really liked Maders as a tourist... it's all what you make of it... don't know Karl Ratzch's though...

I also have been to Mader's (Karl Ratzch's was closed on the Sunday I was in Milwaukee). I've heard KR is the better of the two, but I enjoyed the food at Mader's very much. I wouldn't consider Mader's formal at all -- my jeans and short sleeved shirt were most welcome there, and no one was dressed up. From what I've heard about KR, it's pretty similar.

I also have no gripe about German food, nor about the prices I was charged.

Thanks again for everyone's feedback and suggestions.