I had to drive through the Tenderloin to meet my niece for lunch today but if you keep your eyes on the architecture, you'd never know that this is one of the worst neighborhoods in the city.
From the SF Chronicle:
"Repeatedly described in most tourist guides as "the worst neighborhood in San Francisco," the Tenderloin thrives despite its bad rap. Sure, there are Tenderloinloads of drug dealers, addicts, prostitutes and mentally unstable street people, but if you can get past that, you'll find it is also one of the city's most exciting and diverse locales.
Getting its funky, florid nickname from the days when policemen were paid more to work its mean streets, thereby affording the cops better cuts of meat, the Tenderloin is moving up these days. A heavy influx of Vietnamese families in the last two decades has been instrumental in achieving -- if not entirely responsible for -- its face-lift. And then there are those incredibly delicious sandwiches you can get at the corner markets.
This area is perhaps the last frontier in SF's ever-expanding gentrification trend, and you can still stumble on unpolished gems in the form of incredible cooking, unpredictable bar scenes, independently owned stores and great live music.
The streets aren't the cleanest, and you will be approached frequently by strangers, so just stay alert and don't let it get to you. You have to hunt a little harder for your treasures in the 'Loin, but in a city increasingly headed toward high-end everything, it's a small price to pay."
and more at wiki if you're interested.