I've carried in the St. Tammany area a few times. Used to work in Slidell. Aside from the occasional puzzled stare I had no problems. You're well within your rights and the law open carrying in the state of Louisiana, although some law enforcement officers are unaware of said law.
You shouldn't have any problems carrying. Just understand, it is your right to carry as it is business' rights to refuse service to you (or post "no firearm" signs on the door). If you find yourself in that situation leave and find another place to spend your money as there are plenty of other places that would love to accept it. Just be respectful and you shouldn't have any problems.