Can you eat acorns picked from the street? The streets and parks where I live in New York City are littered with acorns. Can I pick them up and cook them? 

Is it safe? Are they any good? (Taste-wise, nutrition-wise.)
Acorns from which tree?  Acorns from California live oak for instance are edible, but only after a painstaking process of grinding and soaking, without which they can kill you.  European oaks have acorns that are more amenable to eating, but they really can't be eaten raw.  And even the French don't as a rule eat them, which tells me they can't be that tasty :-)