Legal Question in Business Law in California

The issue has not been addressed in California, as far as I know.

I can see in some circumstances that a text message could constitute written notice, and I can see certain circumstances where it would be insufficient. Everything would depend on what the message said, whether the message clearly identified the sender, and what requirements might exist on the form of the message, among other things.

I certainly would not rely on it. I would use certified mail. Unless, you and the other party have an extensive history of texting the court probably won't recognize it. Like myself, most judges probably do not text alot (if at all). Text messages may be held in disfavor. Do yourself a favor: it in writing (keep a copy for yourself) and mail it.