In addition to schoolbuses, there were New Orleans Regional Transit Authority vehicles. According to this, Orleans parish's NORTA had:
Fixed route buses: 364; Fixed route streetcars: 42; Paratransit vans and taxis: 40
What I'd like to find is a chart or a map summarizing what assets were available and where they were at various times. There's a large amount of information in the comments here, so if someone could summarize that it would be appreciated. Note that the first picture at the last link is of NORTA buses, not schoolbuses. And, note that he has a picture of one bus yard... that's empty. I'd also like to find out what happened to what was there before.
There's a start at a bus map here, and a 1.8Meg aerial shot showing at least one bus yard here.
According to this, for the state as a whole:
Automobiles registered: 2.0 million
Light trucks registered: 1.5 million
Heavy trucks registered: 32,000
Buses registered: 21,000
Motorcycles registered: 48,000
Rail transit systems: 1 light rail
Numbered boats: 314,000