While many cities do have leash laws the intesity of enforcement varies from from city to city and even between neighborhoods.
Sometimes leash laws are not enforced due to budget constraints and thus the inability to hire and pay an animal control officer.
While leash laws often state that dogs must be on a leash whenever it is off the owners property it is unlikely that you will be cited if the dog is under voice control and is not bothering anyone. In some cities or neighborhoods police strictly enforce leash laws. This is especially true if they have been receiving complaints about unleashed dogs in the neighborhood. Policy may vary though so it is always best to ask about the customs in your neighborhood.