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.