Exchange currency at your bank in the US before leaving if possible. Many do it for free as a courtesy for their customers, but it usually requires you to do it a few days in advance of leaving..........
Heading into known tourist areas that attract pickpockets with your wallet stuffed with the local currency does not seem like sound advice. Sure, maybe exchange $1000 for some Euros to make small purchases or tips on arrival makes sense but put the big ticket items on a card that has international travel features.
But I'm never going overseas again so it's a moot point.