It's easier drving on the freeways than on the street. I discovered this in England, where the motorways are far easier than the highways (especally on signage). On the freeway the opposing traffic is on the other side of a wall and once you get on the traffic is all in your direction. Just be careful getting on and off. He might also try driving on a quiet side street to get used to the feel of driving on the wrong side, where there isn't a lot of opposing traffic.
Plan ahead. It will help if he knows exactly what route he's going to take before he gets on the road. Mapquest.com is great for this. Just click the link for diirections, input the starting and stopping points, and it will give him step by step instructions. This is especially helpful in downtown areas where there are a lot of one way streets. GPS is great, but it won't give you as much advance warning as having read the mapquest instructions.
A strong word of warning from someone who has driven LA traffic for decades. Don't. Not unless you absolutely have to. It's not fun, the drivers are crazy, and the traffic can congest without reason or warning. Outside of town there are some great fun drives, but in town, take the bus, the metro, a taxi or your feet. If you must drive LA traffic, be especially vigilant. Stay off the freeways during rush hour especially the 10 and the 405. In fact, stay off the 405 altogether if you can avoid it. A massive widening project is going on for the next year, and traffic is likely to be insane.
The same advice for any large city. Once he gets there, he should seriously consider leaving the car in the garage and taking public transit, or walking. This is really true in places like San Francisco, New York or Washington D.C., as they have good metro systems.
Wish him good luck and good driving!
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