I'd go with ADMO in Wrightwood. Depending on when you come it could be snow, but you could trailer the bike down to the desert in half an hour or so. It's still darn cold down there right now though.
If it's not snow you could ride from Wrightwood to Lytle Creek and have a fair good time tooling around there trying to get lost. You could even then cross the 15 freeway and go play up Cleghorn.
See if they have plated bikes, if not you will be taking a chance in some places with just a green sticker.
James and Colleen Tucker.
Aut viam inveniam aut faciam
Beat our time, Los Angeles to Ushuaia 70 days