Do you need Cash??
9/10 places accepts Credit Cards. HOWEVER - Gas stations ONLY take DEBIT Cards. This is very important because you will be screwed if you don't bring your Debit Card. With that said, most blogs will suggest that you don't need cash, and although I mostly agree I would still suggest pulling some out as one of the campsite we ended up staying at only took cash and we were lucky to have a random $20 bill in our wallets.
So, Bring your CC, Debit Card and Exchange for some Cash. You won't need more than $50-$100 in cash.