New Orleans is flat so my 6 speed Giatex folding bike (sometimes for sale on eBay for about $200) works great; it even fits under my desk. The Giatex has a bike bell that comes in handy. You can even get an optional rear rack but I just wear a backpack. The backpack has reflective tape so it helps me be seen; I also keep my water bladder in it.

When I get to work, I fold up the bike, put it in a ripstop nylon bag and slide it under my desk. As a result, my bike's not out in the weather getting even more beat up. Also, scum bags looking for stuff to steal or trash don't have access to it.