Since you were talking appetizers, here is my first take:
I'd do some salmon rolls for the oregon part, perhaps a california wine/beer for the beverage (Or sangria punch and one of the more toxic beverages from Mexico (I cannot drink tequila), a bean dip, plantain chips for the bean dip and Guacamole, salsa.
One item good for hiking that I have no clue on where to get all of the needed ingredients for would be 'Alegris', sort of a mexican snack/hiking bar.
http://www.tamaraduker.com/2009/04/alegria-mexicos-answer-to-the-rice-krispie-treat/For southern Cal, maybe leave out some ingredients for fish tacos?
http://allrecipes.com/recipe/quick-fish-tacos/detail.aspxCome to think of it, add some more expected ingredients for tacos in general.
For mid Cal, I would put out a decent garlic spread (for Gilroy) and some crackers. Or a simple roasted garlic (elephant

)
Not to mention a fruit plate to represent California. (sorry - I had to edit this. I meant that California produces some great EDIBLE fruits and produce. No insult intended to anyone. Mea Culpa)
May whatever deity you worship dislike you if there is California generic cheese. Wisconsin cows are happier and less nutty IMHO.
If you are going for wild things like game, I would suggest something simple like a goat stew and a roast duck salad. Both are readily available, the goat is authentic, and if your group is like my wife's there are more readers than gourmets. Or get goat meat in cubes (how I most often find it in my area), roast it with an olive oil coating and put out with toothpicks and a couple of sauces.
Oh Heck! I just remembered I actually gave the wife a book on "book club menus". She is gone for a while, but I will have to se if I can find it.