No one would want to give advice without seeing the pleading, (and Avvo is for analysis, not legal advice.) You might want to discuss it with the plaintiff's attorney (and confirm your understanding of the conversation in writing) as to what causes of action apply to you. Otherwise, depending on whether or not the complaint was verified, if not a general denial, and if so, admit or deny each paragraph would be the most prudent and conservative approach.
The above is general legal and business analysis. It is not "legal advice" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.
If none of the allegations allege anything against Does or against defendants generally, you could demur on the grounds that the complaint does not state a cause of action against you. If the plaintiff amends the complaint to state a cause of action against you, the statute of limitations begins to run from the amendment, not from the date of filing. Including Does in the complaint but not alleging anything against them is a not-unknown pitfall for plaintiffs.
Ideally, each fictitious defendant should be mentioned in the facts of a cause of action as if the plaintiff knows their true name. So, when the plaintiff ascertains the true name, the plaintiff files an amendment saying "doe 1 is John Smith," etc.
However, "all defendants" can work, too, in some situations -- and agency, alter ego, and conspiracy allegations can link defendants together as well.
As mentioned above, the pleading needs to be analyzed by an attorney.
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