there are two ways you can go about this. I did both. I also live in so cal (san diego).
option 1) use the following website to search for DOs in your area. you can search by name, specailty, city, zip code. etc. I picked like 12 physicians in areas i thought I would enjoy shadowing and I sent each a letter telling them who i was, why i was intersted in shadowing, and a little bit more about myself. I gave them contact information like email and phone number and was called back by almost every doctor i contacted. If you want, i can show you my copy so you can get a feel for what it looked ike. If you are crunched for time, it may be better to cold call the physicians office as opposd to sending letters via snail mail. It ended up working well and i summered an orthopedic surgeon for an entire summer. Here is the website.
http://www.osteopathic.org/directory.cfm
option 2) you can sign up to be part of the ostoepathic association mentor program. this program pairs students looking to shadow DOs who have already volunteered to be shadowed and are expecting to be contacted. it might be easier than cold calling/sending letters, but some peope have complained about turn around time after submitting the request. you can search by city, specialty, and even osteopathic college. A list will pop up of peoplet hat meet your criteria and you select which one you would like to be your mentor and they will be contacted. I did this as well and was contacted very soon after i filled out the paper work. You may try both and see whoever contacts you first! here is the website for the mentor program. good luck!
http://www.osteopathic.org/YOM/mentor_search.htm