I've actually never had to use one before, but I need to wash my King-size comforter, and our machines aren't big enough. Do I have to sit and wait through the wash and then dry? Can I drop it off for wash and fold service? Do I bring my own detergent/dryer sheet?
When I used to go to a laundromat I would leave it and come back when it needed to be switched/was done. But the place was sketchy enough that I figured that the risk of having my stuff stolen was lower than the risk of hanging around there. Your experience may vary.
But yeah, I'd drop it off at the dry cleaner (though warning that if yours is like mine, washing a comforter costs a flat rate of around$30 even though wash and fold is normally $1.60 or something like that a pound and a comforter isn't that heavy).