We dock at 7 am and don't fly out until 5pm. We want to see New Orleans. Are there luggage storage lockers at the Julia cruise terminal?

Right in the terminal, 1st level by thy elevators connecting to the mall... beware of the time to get to the airport, when you come back to the cruise terminal, the rush is over, everyone is gone, etc... very hard to find a cab, you might have to walk out to the main street, if you're in a rush, it will be stressful...

https://freetoursbyfoot.com/luggage-storage-new-orleans/

Yes in the terminal