I drive the 91 from Corona every weekday and Monday mornings are the 2nd best weekday out of the week for traffic (Friday monring is the best). With the price of gas and the foreclosures in the inland empire, traffic hasn't been that bad.
If you leave at 6:00 and take the carpool lane, it'll take you about 45 minutes from the 91/15. If you leave at 7:00, it'll take you just under an hour.
Of course, this is all barring any accidents.