According to the LA Times, it is virtually certain that Californians will vote on a ballot initiative that will make marijuana possession for recreational purposes legal. If the ballot initiative passes, California will join a handful of other states such as Colorado, where pot is legal according to state law but still illegal according to federal law. Medical marijuana to treat a variety of conditions, including "Any debilitating illness where the medical use of marijuana has been deemed appropriate and has been recommended by a physician" is already legal in California.
Simply writing a ballot initiative that makes marijuana legal in California is just the beginning. The difference between an initiative that will be fought tooth and nail by a variety of interests, such as law enforcement, and one that may pass easily with little opposition depends on how the wording of the initiative deals with how a recreational marijuana industry will be taxed and regulated. Considering the experience with the medical marijuana law, it would be best if these matters were decided in advance and not left to the legislature to mull over.
Another consideration for Californians who are anticipating being able to imbibe in their cannabis is how will the federal government deal with marijuana? The current administration has taken a hands-off approach to enforcing federal marijuana laws in states where pot has been made legal. Around the time a marijuana legalization initiative becomes state law in California, a new president will be sworn into office. Will a law-and-order administration clamp down on marijuana? Or will a president, perhaps adhering to the 10th Amendment that leaves many matters to the states, continue the current approach? This is a prime consideration for people before lighting up.