This would be my recommended route but I'm not as au fait as some:
If you want to do it in one day, here are the two routes I suggest.
Both routes avoid most of LA since you are on the 210 Freeway avoiding the worst of the middle of LA, the second is more scenic and kind of fun and doesn't add too much time to the drive.
You could hit "LA" traffic on the 15 Freeway and 71 Highway, but it will be in specific areas and not that big of areas. The only way to avoid it time wise it to leave at 6AM, or take the 15 Freeway all the way to the 215 Freeway and avoid the "cutoff", but that might add as much time as you save.
Play with the Google Maps program, especially the "traffic" feature, it is way cool.
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