AZ 2 member LLC doing business in CA.

I have a 2 member LLC (AZ) doing business in CA.  So far they have opted to be treated as a ptshp but still have time to make an entity choice filing to be treated as a sub S corp. 

If they do the latter (file paperwork with the IRS to be treated as a sub S), would they register with the Sec of State as a foreign LLC doing business in CA or as a foreign corp doing business in CA?  Does the federal election automatically transfer to the state?

What non-resident tax return to file? 

Also, I am trying to weigh the min franchise tax plus the LLC gross receipt tax against the corp min franchise tax and the CA sub S tax!  All the while keeping in mind the SS Tax (or not on some of the income) at the federal level if they go with the sub S and put themselves on a payroll.  Any suggestions?   Thanks!!