If you are not a member, you can not merely join, you must be "taken in."
This can be best be accomplished by finding one of the brethren in a drinking establishment (he will be wearing a red shirt). Offer to buy him a drink or two, or three, and respectfully explain that you would like to be introduced to the Ancient and Honorable Order of E Clampus Vitus. After four or five drinks, if you have thoroughly impressed him with your knowledge of California history, suggest to him that you would gladly and willfully submit to being a "Poor Blind Candidate."
If he determines that you are of substantial character, capable of surviving the ordeal of initiation, offer to meet again next week over a round of drinks, to confirm his sponsorship.