I used to do that, but then I bought a small tripod that folds up that you can easily carry around.Of course with it being dark you'll need to get nice and friendly with the trash cans.
I have also noticed staying late can get you some really nice pics. Even the Photopass Photographers will stick around a little while longer for people.
Also try getting a mini tripod. Night shots are really hard to take without one due to the longer exposures. But this will allow you to get good firework shots if thats what you are looking for.
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