I support Michael's answers below and I use the "must have made 6 payments BEFORE MAKING THE APPLICATION" rule for FHA Streamlines. Borrowers on the loans must be the same unless you wish to start over and lose some of the benefits of the streamline.
I am licensed in CA and can help you directly if you'd like.
You can only Streamline IF all the borrowers remain on the new loan so the co-signer would have to stay on the loan.
The only way to get the co-signer off the loan is to process a regular FHA refinance in which you would need to qualify on your own.
If you move forward with the Streamline make sure you ask the lender you select a)if they require pay checks and calculate a debt to income ratio, b)they require a full credit report. We broker our FHA loans and have found that most, but not all, lenders are requiring a and b. You want a lender that does NOT require those items or you may jeopardize your approval.
If you have other specific questions post back to this forum or you can contact us via our profile.
As for taking off the co-signer, you will need to provide income documents (no appraisal) to do so.