Originally Posted by hiyo

AA and DL are in Terminal 2 in different concourses. http://gothere.com/sandiego/Airport/Terminal-2.htm
Sorry, I don't know if you can go from the AA concourse to the DL side without going through security again. I am always either out of T1 or the Commuter Terminal.

In Terminal 1, the two concourses are separate and a recheck is necessary to go from one to the other, but T2 is completely different in design from T1.

One of the AA FTers from SAN should be able to tell you what you ask.