Surprised no one has mentioned
Sonny Bryan's on Mockingbird. Further than Al's but this is an :-: institution :-:
Free ride from the airport on bus #524, but connection to the other bus is horrible. About 10 minute walk on Inwood.
Ride back to DAL is not free on DART, but if during weekday between 10 a.m. and 2:30 p.m. only $1.75. The whole walk one way is probably 45 minutes.
I walk these routes regularly for exercise