When can you sue on a promissory note secured by a deed of trust? That's a complicated question that deserves a complicated answer, and you can read that complicated answer in this opinion: Ung v. Kohler.
In short, however, it's longer than four years, which is commonly considered the statute of limitations for contracts in California.
Surprised? Check out California Civil Code section 882.020, which courts have interpreted to extend the statute by either as long as 10 years or 60 years, depending on which opinion you read. In certain circumstances, it could be as little as 10 years, but may be as long as 60. So if you think you can avoid paying a house mortgage, guess again. Presumably the statute was enacted to clear title for ancient mortgages where an outstanding note appeared on the property from long ago, and extinguished the note so the new buyers could get clear title.
According the court, it isn't meant to shorten the statute based on contract law, which is what the debtor tried to do here. She got stopped dead in her tracks, and will have to pay the note.