I've only fished a couple of times in the California backcountry, but my limited experience was similar to what has been the general rule in the Rockies. Thanks to the altitude the ice-free season is relatively short, and the fish see relatively few artificials. They are hungry and stupid and will go for most flies, particularly attractors such as wulffs, humpies, adams, and trudes and general streamers such as wooly buggers or mickey finns. But your best bet is to call a local fly shop for advice.
Tight lines, Richard