OP, you've been offered a lot of options and opinions in this thread -- I'm sure more than you can fully process! I sense that your concerns are two fold:

-- you're uncomfortable carrying too much cash out of concerns of theft
-- you've avoided ATMs mostly due to concerns about extra fees and, potentially, just inexperience with them generally

Given that, here's what I'd suggest:

-- Bring $50-$100 in small bills for the myriad of hands that will be proffered in exchange for "service". Just carry it in your wallet with your cards or on your person somewhere.
-- Plan to stop by any grocery store or CVS and get cash back with a purchase using your debit card with it's pin (make sure you know the pin!) if you need more cash along the trip
-- Use credit/debit cards for everything else that might arise

Travelers checks were good in concept (and practice) for a long time but these days they tend to confound most recipients and can come with fees of their own.

Have a great trip!