I'll pass on you some valuable advice we received when we were travelling down to the mouse in Feb/09. I would leave around 8am and get there around 1pm. Any time after 2:30pm the I-5 becomes a parking lot with commuters. So it couldn't hurt to leave even an extra 30 mins early, as it could mean avoiding heavy traffic in the afternoon, and would give you an extra cushion of time if you decide to make any unexpected pit stops along the way.
Thanks for the tip. I'll be stopping by the Los Angeles Convention Center to pick DH up from the E3 Expo (he's out at 5pm so I guess I'll have to find something to do until then) I have not yet mapped everything out...does the I-5 also take me to the LACC or is there another freeway I would take that branches off of it?