This one needs a plain word before anything else. Mecca is the holiest city in Islam, and the area around it, the sacred territory known as the Haram, is closed to non-Muslims. Road signs mark the points where non-Muslim traffic is directed to bypass roads, and the rules are enforced at checkpoints. If you are not Muslim, plan to start your ride from the Taif side or well outside the boundary, and look carefully at where the signed limits run before you go anywhere near here.
The landscape is the reason people ride this way at all. The Hijaz escarpment is a wall of dark rock rising abruptly from the Red Sea plain of Tihama to the highlands, and the road from the Mecca basin to Taif climbs it in a long series of hairpins and sweeping bends, gaining over a thousand metres in a short distance. The Mecca basin below sits in blistering heat, easily forty degrees in summer, while Taif at around eighteen hundred metres is often cool and sometimes foggy. The lower ground smells of hot rock and dust and fuel, the upper ground of juniper and, in season, roses.
Saudi roads are generally wide and well surfaced, but the drivers deserve attention. Speeds are high, lane discipline is flexible, and heavy trucks and pilgrim buses crawl the slopes and make overtaking a gamble. Speed cameras are widespread and fines are real, so keep your documents and your licence handy and obey the posted limits. In the pilgrimage season, particularly around Hajj, traffic around Mecca can be gridlocked for hours.
Fuel is not a worry on the main highways, since stations are frequent, and the nearest community of any size, Al Hadā, sits up the mountain with cafes and small shops. Carry water, especially in the lower heat, and wear proper ventilated riding gear, as sun and wind can drain you faster than you notice. The best time to ride is the cooler months from November to March, early in the morning, when the escarpment is quiet and the air is clear.