I think it's somewhat of a myth that it's easy to establish a wildflower garden...
I would consider checking to see what perennial wildflowers grow (naturally) in your area, pick some that you like, and plant those. Maybe milkweed, black-eyed susan, coneflower, perennial bachelor button, monarda, yarrow, flax (I'm not actually sure that's a perennial, but it is a 'roadside weed' here), old-fashioned daylilies (aka "ditch weed" around here), and, as Daisy mentioned, lupine, columbine, and foxglove. Starting from plants -- either purchased or started yourself from seeds and grown for a year or two -- might also give you a better chance of them not getting overrun by the weeds.
I hope you'll keep us updated on your progress!
