Being born and raised in Watertown, Wis., I can attest to the awesomeness of Glenn's Market. Also, Mullen's Dairy Bar is an absolute must... sundaes, malts, floats... all excellent. Pretty good burgers & fries too. Mullen's isn't a throwback or retro, it just hasn't changed in 50 years (and that's a good thing). Although I haven't been to Zweigs in over 20 years, it served one of the best burgers in town and its broasted chicken WAS the best. Id' be eager to return. In the 60s and 70s, Emil's Pizza was the best, but alas, he closed his restaurant and went into the frozen pizza business, which you can still purchase at Glenn's.
On Main St. is a bar called Amado's, which now serves it's version of Mexican food, which I've never tried, but the reason I bring it up is, my dad and uncle owned and operated this bar as "Tegg's Tap" from the late 50s through the mid-80s. I haven't set foot in it since 1977; might be worth it for a quick tapper or two.
Regrettably, many of the great places of my youth are gone.... The Tip-Up, The Galley (drive-ins) and Dog 'n Suds with carhops on roller-skates! The Sharp Corner was the best German restaurant in the area, the Green Bowl for fish fries, Pagel's Bakery for EVERYTHING (potato rolls, donuts, potato chips & popcorn, pies, etc.) Buehler's and Royal's meat markets (Glenn's has taken over for them admirably) and I wish there was still someplace one could get the famous Watertown Stuffed Goose.
Me and Mrs. Braumeister are 'in' for at least the Watertown leg. See you in June!