That depends on what you're carrying. Not all credit cards have RFID chips, and those that do usually have a contactless payment logo. At this point, only a small percentage of US credit cards have RFID chips, so chances are you don't have anything to worry about. When it comes to your passport however, it's not a bad idea to use an RIFD blocking bag, wallet, or sleeve when you're out and about with it. All US passports since 2006 include an RFID chip that transmits most of the personal information shown on the first page of your passport. When possible, you should really leave your passport in the hotel safe. Taking your passport with you while you explore just opens you up to theft, accidental loss, or scams. If there isn't a safe available, or your hotel is sketchy, it can be more secure to keep your passport with you, provided that it's well hidden and RFID protected.