Let me strongly suggest Azteca de Oro
http://www.aztecamex.com/
I am an Orlando local, and I purchase a coupon each month and have a BIG lunch here.
Very authentic Mexican, great food & service.
Easy to get to from Disney, just north of The Greenway on SOBT.
If you ever drove the Greenway from the airport to WDW, it's the exit where you pass the Super Target, Cracker Barrel, and Home Depot.
One warning about Restaurant.com
MOST of the restaurants are in downtown Orlando, Winter Park, and even further.
Be careful on the location, traveling up I-4 during dinner rush hour can take a LONG time.
Finally, I have never had a problem with any coupon, aside some restrictions clearly specified on said coupon.