StoneMeadow: Good advice, with an exception. You say,
You can go to any MD or OD with a California license to practice medicine. Your doctor will need copies of your medical records, and will register his/her recommendation with the State, along with the number of the letter he/she issues to you.
imo, This is not true. The ONLY State registration is the the optional county program.

And you say,
Dispensaries (and anyone else for that matter) can easily check with the State to determine if your mmj card is valid...
Again, no. The website only validates the optional State ID. There is no reason (that I know of) to obtain a State card.