Both hotels have free wifi (however, service quality cannot be vouched for).
There is a Mobily store (Mobile Phone service) at the base of the Intercontinental Hotel facing al-Masjid al-Haram in Makkah. It is easy to locate. Find the Dar al-Tawhid Intercontinental Hotel and look for the store at the outside base of the hotel. You can get a phone/data sim or just data sim, as you like. As for "GB ma'a Daqaa'iq" (data and minutes) to let the representative know you want both or just "GB bas" (data only for a tablet or if you don't need phone minutes).