Please visit this website below for more information regarding the law and evangelism.
You might have to search in different parts of the website or contact the ministry for more information. They have a very good radio program called The Legal Alert. You may call them and ask them legal questions regarding the law and evangelism.

Christian Law Association
http://www.christianlaw.org/cla/
http://www.christianlaw.org/

The websites below have online articles about the laws in the USA regarding evangelism in public places:

Biblical Evangelism
http://www.biblicalevangelism.com/451

Chick Publications
https://www.chick.com/articles/legality.asp

Educate for Life
http://educateforlife.org/united-states-law-say-sharing-faith-public/
http://educateforlife.org

Open Air Outreach
https://openairoutreach.wordpress.com/2013/04/03/legal-rights-of-street-preachers-how-to-handle-police-jesse-morrell-2/

SOS Ministries
http://www.sosmin.com/pdf/Legal-Issues-Evangelism.pdf

Resources For Evangelism
www.resourcesforevangelism.org
https://twitter.com/Evang_Resources
https://www.facebook.com/Evangelism-Resource-Directory-166006197340504/