If it doesn't show when you're wearing it, you might be able to leave it on. You could certainly put it back on once you're in the park. I just wanted to give you a heads up that if they see anything under the shirt, they will direct you to bag check.
I agree with other people on the boards that it doesn't make sense to search the bags, but allow people with tons of pockets to just walk right in. But that's how they're doing it for now. They do have a guard posted at the "no bags" entrance that looks you over as you approach - that's who would be looking and directing you to the bag check lines if necessary.