Remember "how long" it took the administration to have troops on the scene in Katrina (3 1/2 days) ? My guess is, it will take just about as long in the wake of Rita.
It's a tough call really... I would hope it's sooner, but FEMA does warn about not counting on ANY help for 72 hours on their website. I don't think that's changed. If it's sooner I think the credit will go to local officials - PD and FD.