I've been there as early as 7 AM and it was open. Toilets don't open until 11AM. So go before you go.
If your looking for the places to be open, then call in advance. There are 2 restroom facilities, that i can recall. ROB and Alfred are correct, bathrooms open at 11 am. But the one furthest from the parking lot closes at 4. The one closest to the parking area closes at 3. Go figure !
Dusk to dawn
Don't know time lot opens have not seen it locked but I have arrived only after 9am. Note bathrooms are only open now between 11 and 3
The park is closed from dusk to dawn but the times always change
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