Drugs, particularly marijuana, are widely available in Nuweiba and famously cheap. This does not make them legal, so consider very carefully if you want to risk at best large fines and at worst lengthy prison terms in Egypt's notoriously squalid prisons before indulging.
Women travellers are pretty safe in Nuweiba. As a matter of courtesy to the local customs, even though you will see quite a few girls with short skirts and tight t-shirts, please respect the fact that Egypt is a conservative country, and dress appropriately in the city at the beach a bikini is no problem.
