Lots of good advice posted in this thread. I also use my bike for most of my transportation in New Orleans and do not own a car. I would say that I am "car-free". but I find United Cab comes in handy on rainy days or if wearing a suit on a hot summer day. Our transportation network of buses and street cars also works well for me inside the city, perhaps not so well for some others. However, getting to the airport via public transportation or a taxi is a pain in the butt and expensive. Our transportation system to the airport is locked up by the taxi cab drivers to the detriment of many people. Light rail has been on the drawing board for over ten years but lacks traction. Getting to the Union bus and AmTrak terminal on a bike is much easier than traveling to the airport.

Cycling here, just like anywhere, requires being aware of your surroundings. The relative "safety" of any given street can vary quite a bit from nearby streets, so one learns quickly which routes are better than others. In addition to the recommendations about tires (700x35 Panracer Ribmos for me), I will add that having a good lock is very important. I also will add that, because of the risk of theft, keeping a bike inside an apartment is much preferable to keeping the bike locked up outside or in a common area.

IMO, your friend would regret NOT having a bicycle during her time in New Orleans and she should start shopping now for the "perfect" bike, preferably one with a rack or basket for when she MAKES groceries.