No experience with hay bale construction but you might want to resource these folks :

Penny Livingston at the Permaculture Institute in Bolinas or Pt. Reyes.
I think she builds primarily with Cob, but will probably have more experience than most people in the bay area with straw bale construction.

Michael Collins, aka Miguel Collins or 'Scooby Dooby Dude Smoke 'em up Mikey' is another out of this world contact for alternative innovative building techniques.
He's a hard one to find though and often goes to Mexico for the winter, otherwise you can find him up on the Coleman Valley Road Commune in Occidental .
You'll just love this guy , he's a one of a kind !!!
The name of his biz'ness is Biotecture or Biostructure.

Another resource to further check out is Green Gulch Farm Zen Center on the way to Muir Beach.
They built a really beautiful straw bale potting shed/ nursery office 2 years ago and will probably have some good resources.

Question - why straw bale ?
Does it relate to the architecture / landscape architecture in some way or the clients environmental philosophy ?

There will be a cob seat-wall building class at Strybing Arboretum (yes, I know the official name is San Francisco Botanical Garden) some time in the spring, FYI.