There is no reason to blame New Orleans officials. Here is a link to the forecast advisory for 72 hours before landfall. The NHC was calling for a 90 knt storm to be at 86.5 on Monday morning. That's a category two over 180 miles to the east.

No one should call for a full evacuation on that report. The first time they showed New Orleans as a target was late Friday night, just over 48 hours until landfall.

http://www.nhc.noaa.gov/archive/2005/mar/al122005.fstadv.011.shtml?

Edit: Friday night was about 60-63hr prior to actual landfall, not just over 48hr. You can make the argument that the period of reasonable conditions to get people out was closer to 48hr, however. --Clark