The List has long given Jerry Garcia and Merl Saunders at the Aztec Bowl, San Diego State College (I think it was still this C and not a U at the time), November 18, 1973. Because Garcia and Saunders had barely played out of the Bay Area by that time (Ash Grove in LA 5/29-30/73, the Hells Angels show on 9/5/73, John Scher's Passaic Capitol Theatre on 9/6/73), it would have been pretty noteworthy, had it happened.
Like the canceled show at the University of Iowa on 10/20/73, it would have made some logistical sense, dovetailing nicely with Grateful Dead gigging. Also like it (and another early out-of-town show, 2/16/74 in Passaic), however, it appears not to have happened.
Most importantly, despite this being a putative show in a football stadium, I have never seen any eyewitness accounts. Doggie no barkie.
It appears to have rained in San Diego on 11/18/73, less in town than the biblical 4.5" received in the Palomar Mountains, but having just seen S.D. responding to "rain" the last few days, even a half-inch or so may have been enough to scuttle the whole thing. I believe there may have been Aztecs soccer and/or football events planned for the turf, and maybe they didn't want a bunch of rock fans mucking it up.
That makes sense, but the weird thing is that, besides the door listing reproduced above, after a little poking around I have found no mention of the show in either the San Diego Union or, more problematically, in the SDSU Daily Aztec (digitized, albeit with a rather clunky interface, via the University library's digital collections). I do not understand why the show would have been listed in the door published on November 8th, but never mentioned or advertised in the campus paper.
Thoughts about this? Either way, I am about 99% confident that the show never happened, probably one to strike from The List (now, our individually-maintained lists) of Garcia shows.