It turns out that the jury was instructed on SYG (jury instructions 
here), but I can't imagine a single account of the facts in which it would have applied.
In  the state's version of these events, Zimmerman either started the fight  or threatened Martin. If SYG applied to anyone here, it would have been  Martin, but regardless, Zimmerman would have been engaged in illegal  activity. Or, there's an alternative version where Martin started the  fight and was beating Zimmerman, but not to such an extent that  Zimmerman reasonably feared death or great bodily injury. Here,  Zimmerman is permitted to use force, but not deadly force, so neither  SYG nor even basic self-defense is any help to him.  (Note that in the  first version, the prosecution is required to prove beyond a reasonable  doubt that Zimmerman started the fight or threatened Martin; in the  second version, the prosecution is required to prove beyond a reasonable  doubt 
Zimmerman's state of mind. The impossibility of proving  any of this, given that the two best witnesses were dead and entitled to  invoke the Fifth Amendment, respectively, is why Zimmerman was  correctly acquitted.)
In Zimmerman's version, Martin started the  fight and Zimmerman didn't kill Martin until Martin was on top of him  and beating him, so he had no opportunity to retreat safely. (The bit  about Martin being on top of him is almost certainly true, based on the  testimony from the defense's gunshot wound expert.) Self-defense in this  situation is allowed in all fifty states, not just the ones with SYG  laws.
The widespread idea that SYG is an integral part of this  case, much like the widespread idea that Zimmerman was obviously guilty,  is rooted in early news accounts of the case that didn't prove  accurate. The sad irony is that if someone was deemed ignorant enough of  the details of this case to serve on the jury, SYG was probably one of  the few things they'd associate it with. It's worth noting, too, that  four of the five other jurors released a written 
statement to the effect that B37 shouldn't be treated as any kind of spokesperson for the jury as a whole.
If you think the waiters are rude, you should see the manager.