I agree with SRen. Renting a small car would probably not cost much more than the cab fare to and fro.
Would agree with the two above posts, with the difference of getting off at the Milwaukee Airport (MKA) stop, taking the free shuttle to the airport, rent a car from there (More selection and competition, which makes for a better price) and you can drive around the outskirts of town as opposed to dealing with downtown itself.
You might want to mention how often the Badger Bus runs and if you know the timetable state it as simply as possible.
Is there bike racks on the transit buses?
Are you thinking of taking in a tour at Kalmbach?
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-Crandell