Hi, I used to live in Egypt and did so for 4 years. You do have to be careful what you wear but mainly out of respect of their culture and religion. You can wear strappy tops or even backless tops (women of course) but not in a Mosque! You just need to use you noddle! If you are travelling to egypt for the first time you need to pack; insect repellent - lots of it, sun cream, a good hat, and a very comfortable pair of shoes - you will probably do a lot of walking in the hot sun! Also a pair of long trousers - if you intend to ride a camel! A phrase book is always handy even though most egyptians speak English and are proud of it too! Make sure you have some Egyptian cash and your credit cards. Remember to barter for 90% of goods especially if bought in down-town Cairo, even if you pay with Credit Card!!!
Enjoy have fun and I hope this is of some help to you. You can contact me again if you need any more info.
Regards, Clare.