Just ask what kind of car they drive, and if you can borrow it? Another good way to gauge a guitar cadge is to ask them if they have a pick. Chances are, anyone walking around with a pick, can pick and will rewpect your instrument. I suppose the flippant answer is to reply that the instrument doesn't actually belong to you, but rather to the credit card company. I had a Sindt whistle stolen two weeks ago by a casual "borrower" at a friendly Irish session and am strictly non-lending for awhile.