This is one of those circumstances where I am forced to be the bearer of bad news. I hope you don't decide to "shoot the messenger." In Kirschenman v. Superior Court (1994) 30 Cal. App.4th 832, the California First District Court of Appeals held that "the [Superior Court has] no statutory authority to require the parties to participate in mediation." Id. at 835; see also, Lu v. Superior Court (1997) 55 Cal.App.4th 1264, 1270 (interpreting Kirschenman).
Parties who agree to mediation in a contract may waive their right by filing a civil action, rather than requesting mediation. If you want to try to make a new exception in California law, then the proper procedure would be to file a "demurrer," to the landlord's complaint, point out that the contract requires mediation, and that the landlord has not alleged that mediation has taken place and failed, therefore as the landlord has not stated a claim for which relief may be granted, the case should be dismissed.
Alternatively, you could deny the landlord's claims in your PLDC010, and add, "condition precedent: mediation" as an affirmative defense. Then, assuming that you were to prevail in the case on your affirmative defense, the landlord would be required to mediate. This would be a legal means to proceed with the case, but you would have to litigate the case to a conclusion, which would be extremely inefficient. Thus, the demurrer option is, in my opinion, the preferred choice.
Note: If you don't understand the concept of a demurrer, there is a pretty good article on the subject at this link:
If you need more comprehensive assistance, I can send you an additional services offer, and we can take this matter offline -- however, I would have to charge you customary legal services fees, so this may not be cost-effective for your circumstances.
There are also a number of professional civil practice guides that can show you how to draft a demurrer. You can find them all at your county public law library (or, you can purchase one, but they're very expensive). If you need assistance in locating your public law library, or you want a link to a professional practice guide, please let me know and I will be happy to provide.
I realize that my answer may not be exactly what you were hoping to read. However, under the circumstances, the best that I can do is to explain what the law is and is not, so that you can avoid expending valuable resources looking for answers that do not exist, and concentrate on the options that are actually available.
I hope I've answered your question. Please let me know if you require further clarification. And, please provide a positive feedback rating for my answer -- otherwise, I receive nothing for my efforts in your behalf.
Thanks again for using Justanswer!