I do not recommend waiting until you go to the RAC desk to do your SWA check in as that means you are checking in only 12 hours before your flight at the earliest. That means everyone who did EBCI or checked in starting at 24 hours is ahead of you. While there are some posters who have indicated that RAC (it's NOT Disney) checked them in at the 24-hour mark and there are some who say that this is supposed to happen if you used DME on the way to your resort (but maybe subject to certain other limitations, such as if your flight is an a.m. or p.m. flight), I have not seen enough evidence that I would rely on RAC to check me in before I was at the desk.
As a result, we always use EBCI for our return trips; as much for the convenience factor as anything. If you don't want to pay the extra $10 per ticket for EBCI, then you can have the front desk at any Disney resort or the guest services locations at any of the parks or in DTD do it for you, you can do it yourself with any Web-enabled cell phone or other device at mobile.southwest.com, or you can arrange for a trusted (100 percent reliable) friend or relative to do it for you.