So long as disclosed in the note and plan documents, yes you can accelerate and declare entire amount due. Since line of credit, obviously only what has been borroweed can be demanded.
However, Arizona has an anti-deficiency statute that applies in most instances, meaning you cannot sue the borrower for any deficiency from the foreclosure sale and with housing prices having tanked here, I bet the house is under water.
Check the home value and first mortgage balance before you move to foreclose.