We have done this same thing, and plan on DL before our
DCL in October. You can catch ART (Anaheim Resort Transit) at the end of DL by Harbor St (where all the busses let the people on/off for DL). I'm not sure which #, but there are transit maps. Take the one to AMTRAK. Then catch the train to San Diego. Super easy, and no transfers if you get the right train. Inexpensive as well. Leave the SD train station, and head to the water. B Street Pier is right there, 2 blocks down, and 1 block to the right.