Anyone can watch the fireworks from the poly beach any day of the year including July 4. We have done it most years since 1992, and Not once have we seen or heard of a real case where someone was sent away. Yes, you are not allowed to use the pool, and you can not park unless you are staying or dining.
In fact this year, they added a food service cart on the beach selling hot dogs and drinks. They had it out both July 3 and 4. They are capitalizing on all of the added people. This may have been there last year, but just didn't see it.
We do usually have a dinner reservation, so we do get to park, but once on the beach, no one knows who is who, and no one ever checks. There are added gaurds around, but that is just for general safety. They do not check anyone.
George