AFAIK, www.stc.com.sa have at least branch or two at almost all airports and they have the best coverage and service within the Kingdom. They'll help you setup everything on the spot. All prepaid services require ID registration, not sure if that changed recently.

Wifi is greatly available in almost every hotel/cafe/mall and you won't have trouble connecting if your visit is short. I've noticed client sites are also well equipped with excellent wifi service.