Dumb idea.
The problem is getting solved as fast as it is going to get solved, and Bush is not wasting one minute on blame. Telling people to shut up for two weeks solves nothing, it just lets the really culpable people (Blanko, Nagin) coodinate their stories.
If you feel so stronly that shutting up for two weeks will make a difference, I suggest you don't need a presidential proclaimation to act in accordance with your beliefs.
Perhaps I didn't make myself clear: It's obvious the blame game comes from the Left. It would be politically wise for Bush to call attention to it and point out how detrimental to the recovery & healing process.