BE sure to pay attention to what Border_lord said about calling your banks and credit card companies to tell them the dates on which you will be in Egypt!!!!!! I to do that last year and had to make a couple of very expensive calls back to the U.S. to the bank to get my account and credit card authorized for use in Egypt!! (so embarrassing that I that...
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A money belt or a travel wallet that is worn on your body under your clothes is advisable because of carrying large amounts of cash. The usual cautions about keeping your bag, purse, backpack, whatever in front of you when in very crowded situations. While Cairo (and Egypt in general) is not as crime infested as many US large cities, there are pickpockets who might take advantage of very tightly crowded situations.
My friend and guide Ahmed or his son Karem can take you to Yasser's which is much harder to find than Mahmoud's. (see Amity's blog).
Say hi for me to Mahmoud, Yasser, and Amira if you see her.