There's a place a mile or two from the Harley Museum called Sobelman's which is renowned for burgers, beer and Bloody Mary's. Good Mexican food abounds to the south, just across the river from the museum. There are fantastic frozen custard stands all over town, though I can't think of any offhand in the downtown area. Leon's is the iconic place for custard, but others are just as good.

Several decent places line Water Street, about a half mile east of Harley. AJ Bombers has some of the better burgers in town, Smoke Shack has good, though pricey, BBQ. Water Street Brewery and Milwaukee Ale House each have a nice craft beer selection along with above average food. There are also a couple of small breweries and distilleries nearby that offer tours, if you're into that sort of thing. The granddaddy is the Miller Brewery tour, about 15 minutes from the Harley Museum, depending on traffic.

About a half mile northeast of Harley is the Milwaukee Public Market. It's nowhere near Philly's Reading Terminal Market or Cleveland's West Side Market, but has some worthwhile stands.

Give me an idea of what you like and I'll try to be more specific.