The texts of bills after 1999 are readily available from the California legislature's LegInfo website:
For bills between 1993 and 1999, you'll need to use the California legislature's old website:
Finally, many pre-1993 bills have been scanned and made available online for free by the UC libraries, California State Library, and Stanford Library:
Copies of bills are also available at the law library in microfiche:
If you have not used microfiche before, feel free to ask a reference librarian for help.
Older bills are available in print from the Southern Regional Library Facility, a storage facility located on the UCLA campus:
Most bills available on Lexis and Westlaw are available and easier to read on the California legislature's website, so there is usually no advantage to accessing bills on Lexis or Westlaw. However, Lexis is sometimes useful for bills between 1991 (when Lexis' coverage starts) and 1993 (when the California legislature's website's coverage starts).