Not as bad many may let you to think. Going in/out north Irvine is worst than south on the I5, and to/from La Jolla is a nightmare.
Depends on which part of Irvine--my aunt lives near UCI and that's the 405.
Even if he have to take the 405 it ain?t that bad because it is only for a short distant, unless there is an accident. The 73 is not going to be much faster than I5. Sometime it is easier to cut across Culver or University/Jeffery to the I5, and do not take the Jamboree/261 to I5 at rush hour because I make that mistake a few times when I was down there for 3 months.
PS. I just got a job offer there yesterday and I'm not leaving Victoria BC, because it is much nicer here. (Commute to/fro any where in Victoria is 15 min or less, beautiful environment and the people is much nicer).