16th Street is pretty shitty for tacos, no doubt.  But if you were a gang member of the MS-13, the gang that controls the northern part of the Mission, would you consider the limited selection of tacos crappy enough that you'd cross into enemy territory for a delicious 24th Street taco?  According to the SF Weekly, they do just that.  In the Weekly's “Insider's Guide to the MS-13 Gang,” members would “dash” onto 24th for tacos:

10. You can cross into rival gang turf — for a tasty taco.

In one of the more bizarre moments of [former MS-13 member Abraham] Martinez's testimony, he said he'd venture into the heart of [rival gang] Norteño territory on 24th Street to get food at one of the taquerias. “I'd make a dash for it, in and out really quick. Or I'd have someone go for me.” Try Yelping that.

In a follow-up post, they looked into the court transcript to see what taquerias are worth the risk, but there weren't any good answers:

Phillipsborn: There are some taquerias on 24th Street you like? There are times you'd go in disguise to get some food?
Martinez: That's incorrect. I'd make a dash for it, in and out really quick. Or I'd have someone go for me.

The Weekly conjectures that Martinez would head to El Farolito, Taqueria Vallarta, or La Taqueria Guadalajara.  I'm pretty certain it was Papalote.