Only if people plan ahead and make some attempt to help contain the disease (wearing masks, limiting non-essential indoor stops, social distancing), which it's now been proven we can't rely on (at least in the US).

Unfortunately the people who feel most comfortable leaving the house are the people who are least likely to take precautions, which seems like a recipe for lots of super spreaders to me.

Only for locals.

For everybody who drives to the beach (the vast majority of beachgoers), empirical evidence from California beaches suggests that the answers to all those questions is "yes".

If you want to open the beaches only to those who can walk or bike to them, sure that's probably okay. Now, how do you enforce that?

So, we're back to simply closing the beaches completely because it keeps the idiots at bay and is easy to enforce.