Am not sure , I guess but is better to find out
You can use speaker unless security sees it or someone complains about it.
You can bring a portable speaker. I did that yesterday. Wasn't a problem.
No they won't let you in with a speaker
Not sure what you mean when you ask "can you plug your speaker in the park?" Do you mean electrical power outlet for charging purposes? If yes, they have a seating area equipped with USB ports but NO power outlets that I witness. Hope that was helpful!
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