Car rental isn't a practical option in Aswan since you can walk between downtown attractions, and most other sights (Philae Temple, Kalabsha Temple, Elephantine Island, West Bank attractions) involve a boat transfer. It’s better to negotiate a taxi rate, or reserve a private car and driver, and ride with someone who knows their way around the town.
Individual foreigners traveling out of Aswan must travel in a convoy, if headed to Abu Simbel, or obtain police permission at least 24 hours in advance for destinations north, such as Kom Ombo or the Daraw camel market. These arrangements will be made for you if you are traveling with a tour company or a private car and driver. Convoys south to Abu Simbel depart at 3:45 am and 11 am, from a central location, which means your tour company or driver will pick you up at your hotel even earlier.