They say don't put the starts out until June but I always fudged a little, like May 1-15. The ground is usually warm by then. You can get sweet potatoes now or in a month, they get harder to find in a store the longer winter goes on. Make some notes of dates etc for next year, your mileage may vary, as they say.
They will root stuck halfway into a glass/jar of water or laid on the side half buried in a box of moist sand. It does take a while for them to start and hard to say but you might average 10-12 slips per 'tator. They will have long roots if you use water so spread them out when you plant.

thanks rockguy for the information. I have already bought the sweet potaoes I'm going to use for the sprouts. I may put some in water, and a few buried in old sawdust or compost.
thanks again
Tom