Rule number one is to know the neighborhood. Getting mugged by a street gang or shot by a cantankerous resident can ruin your whole day. Respect private property. State laws regarding what constitutes public and private waterways are not always clear. If a property owner objects to your presence, leave.
Many streams run through golf courses, but a hatch of Titleists can be very painful.
Dogs may not have fences between their yards and waterways, and snakes thrive near bodies of water, even in the middle of cities. Many urban waterways are small, so plan accordingly. Seven to eight foot rods from 2-wt. Nymphs, small bass bugs and streamers work well in most locations. Wading boots with felt soles are essential, since urban stream beds tend to be algae covered.