DONT RISK IT, PEDAL YOUR PEDALS
i would wait until the papers and plate come before really getting out and riding. usually if i am just riding around my neighborhood i will tell the cops that i am repairing the bike and test driving it. that usually works for local riding of my not yet registered mopeds. if you want to go farther than that, watch out! cops in california know as much as your local dmv office about moped laws. any hint of something shady will spark their interest. but since they know little to anything at all, once you show them your california plate and something with california dmv information on it, they leave you ALONE!
the good news is that california laws are very lax and so are the cops. for the most part, mopeds arent that big of a problem, so there is no real set protocol or system that is used when pulling over riders. meaning there isnt going to be any chp radar sting operations on mopeds so you shouldnt have to worry. other than title/registration issues cops can really only pull you over for moving violations or emissions/street modification legality (like if you have performance parts on your moped that alter its street legal classification). so, as long as you have your registration and plates and ride smart, you should be ok!
my advice is if you are worried about getting pulled over in california have your registration card and plates with you at ALL times. also, just be on the look out for cops! most mopeds get pulled over because cops are confused, they think its going too slow for a motorcycle or too FAST for a bicyclist... unless you are doing something completely stupid, you should be fine. and if you see a cop PEDAL!!! you want to show the cops that you are a MOPED and not a small motorcycle. even more important, you want to look as less intimidating as possible, I.E. PEDAL YOUR PEDALS AND LOOK LIKE A BIKE!!!!
DONT RIDE WITHOUT PAPERWORK AND PLATES
if you are cruising around your hood for a short ride just tell the cops you work on old mopeds and you are repairing it BUT if you decide to go on long rides, wait until the papers and plate come.
BE SMART, RIDE SMART
if you arent doing anything dumb like showing off your new racing parts on the street, cutting off cars or wheeling by cops at 60+ mph, the only real reason they have to pull you over is because of title/registration information, so have that on you at all times. if you see the cops follow standard road speeds and laws.
PEDAL, PEDAL, PEDA
cops, like the local dmv office, dont fully understand mopeds. they dont know the laws and frankly they dont really even know what makes a moped a moped. to emphasize that you arent a motorcycle, PEDAL YOUR PEDALS. this makes the cops less intimidated by you while also showing them that you have pedals which means you couldnt be a motorcycle. when they see this, they leave you alone.