I lived in NO until three years ago, so I have 45 years of experience riding there. Security isn't a big problem. I would cable lock my bike downtown often and never had a problem. The only bikes I knew of that got stolen were stolen from people's houses.
Weather is problematic two ways: rain and heat. Some rain gear that you can pack away (like Frog Togs) is a good idea. There is no solution for the heat other than to get used to it. I love hot weather so it wasn't a problem for me. Until you are acclimatized beware of getting overheated.
It's not a bad town to commute in, but traffic can be a bit rowdy. Rush hour traffic is heavy but pretty orderly.
What part of town are you looking at for housing?
You should think about joining a gym. There are many hazards to your health, like Mandina's, Commander's Palace, Cafe du Monde, etc.