Mike, the best time to graft these here would be in late spring in May. That would be the best time for people to try and get scions sent to CA. I wouldnt bother trying to order from Hawii now, wait until spring and do it right so you dont have to do it twice. Look at their website, theres probably a contact, I know they had a list of cultivars available on a website or it may have been a thread on here.
When you graft the lychee, you need to cut back the tree around the scion and give the energy to the grafted part or it will not take off. Also the wood is pretty stiff also so you want to keep your graft pulled really tight and leave it for many months to heal all the way or they split. Use an extra strong tape over the graft tape to keep it tight.