Cairo is loaded with historic hotels in the city center that can be great bargains. You’ll almost always be walking through a metal detector as you enter, but you get used to that. Room rates are generally very affordable for hotels that are quite nice, even if they are a bit dated.
Larger, chain hotels are mostly clustered along the Nile and they can be worth the extra money if you are the type who feels uncomfortable in exotic, foreign cities. You’ll pay a lot more for a Nile view, but rates can still be reasonable and it might be worth it.
Hotel seasons in Cairo closely follow the weather, with peak prices usually from December through April, and the lowest prices of the year from June through August. Especially for the winter holidays, if you know you are coming then you are advised to book as early as possible.
Prices can fluctuate greatly at the high-end international chain hotels, but prices tend to be fairly stable at the local and independent chains and hotels. Often a 2-star hotel in downtown Cairo used to be a fancy place that has become a bit worn out, so you can save a lot of money if you are willing to stay at a place that’s seen better days.
It’s not difficult to find a hotel room once you arrive, but the taxi/airport situation can be treacherous so if you don’t have a place reserved to be taken to then there’s no telling where you’ll end up. Booking at least your first night in advance is probably worthwhile.