There are several websites where you can search for medical writer jobs in California. Here are a few:

1. Indeed.com: Indeed is a popular job search website where you can find many medical writer job openings in California. You can filter your search by location, job type, and company.
2. LinkedIn.com: LinkedIn is a professional networking platform where you can search for medical writer jobs in California. You can also connect with recruiters and hiring managers to increase your chances of finding a job.
3. Freelancer.com: Freelancer is a platform where you can find freelance medical writing jobs in California. You can bid on projects posted by employers and work on a project basis.
4. Glassdoor.com: Glassdoor is a job search website where you can find medical writer jobs in California. You can also read company reviews and interview questions posted by other users to get an idea of the company culture.
5. Medzilla.com: Medzilla is a specialized job board for the life sciences industry, including medical writing. You can find many medical writer jobs in California on this website.

These are just a few websites where you can search for medical writer jobs in California. It's a good idea to create a profile on each of these websites and upload your resume so that recruiters can find you. Good luck with your job search!