I use to work in Dahab.. some suggestions
Nessima: More expensive, lovely breakfast, nice swimming pool, a lot of french people. CMAS center also.
ORCA: I love this guys! TDI facility... if you fancy trimix in blue hole... contact them....
Divers Down Under: Peter Dive Center... many koreans and japanese people. But nice, in the center of the bay.
Sinai Divers: you have 2 options, backpackers, near the bridge... near Divers Down Under... or in the Hilton. In the Hilton (I use to work there...) is more expensive, has a little dive site in front of the hotel. (quite crap...) But the Dive Center is really ok.
mmm what else...
Nirvana is nice people....
You can also go to Francois in Red Club... great guy (the manager)... nice location... if you go you have to eat in the restaurant in front.. ask for chicken and pineapple sandwish...
Also Dessert Diver ... you can also do a Freediver lesson with Roland there...
Any way, hope it helps... be carefull with Dahab.. i went for 3 days... I stay there... 8 months.
rofl