lunch time and freedom of speech

Unless PR has some specific laws about it, yes. Freedom of speech relates to the government, not your employer.

 

Your employer can choose to fire you for things you say on facebook or anywhere else, absent a contract to the contrary.

 

OP, you were having a conversation with whom?

If (1) you were having a conversation with a coworker and (2) said conversation related to conditions at the job, then your employer could potentially violate Section 7 of the National Labor Relations Act if it takes adverse action against you for engaging in such a conversation.

If the foregoing conditions exist here, then you should consider contacting the General Counsel’s Office of the National Labor Relations Board to petition for unfair labor practice charges against your employer.