You can book an AP ticketless package where you book a room and add the dining plan without any additional ticket purchase. Now there is a caviate to this. You must book an AP rate or else pay rack rate in order to do this. If you're trying to use any other kind of discount then no you can't add a dining plan without a ticket purchase. If you do have to add a ticket then you're only required to add a 1 day ticket (unless you're booking free dining in which case you have to purchase 2 day tickets).
Regardless of which approach you take to adding a dining plan, you do have to add the plan for the duration of your reservation.
As an AP holder, you are eligible to purchase a Tables In Wonderland card which will give you 20% off your TS meals and 20% off CS meals at AK and value resorts. Most AP holders find this to be a better deal than paying for a dining plan.