I'm another new guy, but I'll answer your questions as best I can.

How hard is it to get a Mj medicial card

California is generally considered one of the easiest States to get a mmj card in.

Once you have Medicial card can you start growing ur own

Yes, you can register with a dispensary to buy mmj in and you may grow your own with no delays I know of once you have the card.

What is the best county to raise family and grow

Where is best for you is a private decision that will be driven by how you like to live (urban or rural), what you do to support yourself, cost of living (generally higher here than in Florida, I think). The counties north of SF are VERY rural and much lower cost to live in than our urban areas and southern counties, but work is very hard to come by up there.

Can you sell what you dont use to dispensires

Yes, but as far as I know dispensaries are not obligated to buy from you. Also, Cali will vote on Prop 19 in two weeks to legalize recreational mj for adults. If Prop 19 passes the entire mmj market will be in turmoil, because no one knows what prices will do.

Good luck!