I've never been particularly fond of the museum itself, and I'm not familiar with the collection, but when I first saw the garden ~9 years ago, I enjoyed it a great deal. Irwin started out as a installation artist and it shows.
I have tried to find photos that capture it, but it really must be experienced: the views in every direction change significantly as you traverse the path.
Here's a shot from the Getty web site

a nice image from flickr

and two of the nicest ones from Paula Panich a writer/writing coach


who is coincidentally giving a writing workshop at the Getty in September.
I would be remiss if I didn't mention Irwin's work at the Dia Beacon

which is also impressive albeit not as all encompassing, but much closer to those on the east coast.