as already suggested to you by someone dahab is the best place i believe in the sinai coz its dirt cheap and still relatively uncommercialised. you can rent a rooom at say bishibishi or lots of other resthouses on the main road in dahab for as little as 20 LE. then u can go to blue hole an amazing place for scuba and snorkelin. besides you can also go to MT Sinai from here at just under 50 LE. and then for the night just hang out at TOTA this is a BAR absolutely free for foreigners and then bet of them.
i think these would help.
besides if you are stayin for more than 5 days in CAIRO i sugggest you buy your stuff from SAUDI supermarket the rates over there are like what you would find in a walmart and you go there by a metro.
i toured egypt last yr and its a hell of a place
for places you could also go to Canadian hostel near Tahrir. tahrir is the best place to be coz its kinda the centre and easy to go to other places. you should also visit the old cairo and then they have a park over there i forgot the name but its pretty good the sights if you view if you go there in the evening and stay till 7ish