I Just came back yesterday, you can see some of the photos taken here :
http://www.flickr.com/photos/ben-bsh/sets/72157632552867686/
I took my 400d, 18-55 and 70-200 (f4 L), and think I would of benefited well from a 50mm prime for the market, as I struggled to get decent shots, without drawing too much attention (long lens) and getting enough light (the old town Market comes to life at night, f4 and my 400d doesn't handle ISO well)
Others have said to watch out, personally I am not a big guy, and felt fine walking round the market / beaches at night with camera in full view, everyone said hello was very friendly.
couple of tips, if you do want some nice shots of people at their market stalls (all mine came out badly for light / ISO settings, very silly of me!) negotiate a price first, in coins.. they will want 30EGP (£3) or something stupid, just walk away. Many realise 50p or £1 is better than nothing and let you snap away, but prices have to be negotiated BEFORE taking photos, and then stick to your guns if they want more.
Same as said above for animals, taking a photo of a camel will cost you, letting them take a photo for you will cost you.
and for Cairo, its perfectly safe, they only run the excursions on days people are not demonstrating (tues and thurs from my memory) and I thoroughly recommend going, and if you can take the "VIP" option with a private taxi and tour guide, do it. get out the taxi and explore on foot every now and again!
I would recommend the VIP cruise Thomson offer, it was an amazing day, i took a GoPro HD with me, but am yet to dig it out and see how the shots underwater turned out.
either way, any questions just ask! have a lovely trip!