It helps sometimes.
There are a lot of knockoff plates 11-99 out there and the officers know that. When you donate to the foundation, they send you a piece of paper that shows your membership, and you're supposed to hand that to the officer with your I.D, Insurance, etc.. Some might give it some weight if it wasn't a serious infraction, but don't think of it as a complete 'get out of jail free card'.
(lol Phillip, your post wasn't there when i clicked reply... my sentiments exactly.