(a) The hearing of a contested case shall be conducted:
(1) In the county in this State in which any person whose property or rights are the subject matter of the hearing maintains his residence;
(2) In the county where the agency maintains its principal office if the property or rights that are the subject matter of the hearing do not affect any person or if the subject matter of the hearing is the property or rights of residents of more than one county; or
(3) In any county determined by the administrative law judge in his discretion to promote the ends of justice or better serve the convenience of witnesses.
(b) Any person whose property or rights are the subject matter of the hearing waives his objection to venue by proceeding in the hearing.