I remember the same question being asked before and sure enough when I did a search at the bottom of the page, up came the thread I've linked to below, but with no answer a year ago either.

I know you've posted in the Vegetable Forum, but have you also posted in the regional gardening Forum that includes California?

Do you know that sweet potatoes are grown in CA? If so, it seems that a call to your local extension service might be helpful in terms of locating some plants.

Carolyn

Here is a link that might be useful: Sweet Potatoes and CA

I do not know the particulars of why one cannot send them to CA, but when i lived there for 45 years, we always started them from sweet potatoes ourselves in the school and at home.
We used store bought tubers. I do know that many do have sprouting inhibitors, but i always found diverse varieties of potatoes and sweet potatoes at Natural Foods Cooperatives. I could choose from perhaps 6 exotic to us taters and at least a couple unnamed sweet potatoes. Slips are so easy to grow yourself and produce alot of plants with very little effort.
Good Luck!
Toni

Don't you have alkaline soil? I remember that someone in Houston TX said that sweet potatoes didn't like their alkaline soil, but that years ago there was a local variety that had veins all over it like on a man's arm. He said that was the only kind that liked it there. I think if you go to a big oriental grocey store, you will be able to find this kind of sweet potato, and some others as well.