Personally, I would go during winter. That's mostly to avoid crowds. It's busy during the summer. And often during the fall is when schools take field trips there. It's obviously colder, wetter, and more of a chance of rain during winter. But I am not a fan of crowds. I also love the wet foggy type of weather as well. That's my opinion. :)
I visited in March, and arrived as soon as they opened. The sound of the brook and the sunlight slanting through the trees was enchanting. We were leaving as a bus loaded with Japanese tourists arrived. Here today, gone to Maui.
It depends. In summer, the weather is sort of hot, but the place still looks beautiful. Maybe not for jogging. In fall, once you walk straight through the park, there is no one.
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