I would allow about 1 1/2 hours to account for traffic. If you have to be to work by 8:00 a.m., then I would leave for work no later than 6:30. By giving yourself this much time you will probably have about 15 to 20 mins to spare once you got to work. But if there is an unexpected accident then you will arrive on-time and your boss will be happy. As you travel from Victorville to Riverside, if you take a straight shot down the 15 south to the 91 east traffic usually backs up around Ontario Mills. Then it backs up as you get close to the 91. But whether you take the 215 south to the 91 or the 15 south to the 91, I would still allow the 1 1/2 hours. For 4 years I commuted between Victorville and Corona/Riverside and that is what I encountered.
Michael G. Grimm