Welcome! San Francisco is amazing. You picked a great city. The Tenderloin, however, is one of its roughest neighborhoods. Be prepared to see humanity at its most raw -- lots of homelessness, mental illness and urban blight. Watch out for petty crime and be aware of your surroundings. That said, the TL is very close to the financial district where you'll be working and has really easy access to public transit via MUNI and BART so you can get around the city easily.
I think you'll find that urban life in America is wonderful. You have everything you could want in terms of dining and entertainment in close proximity. The only catch is that you end up spending a great deal more money on everything, too. One of the perks of the city you chose is that right outside the city, you can explore just about any landscape you like; deserts, beaches, forests, vineyards and most cost no more than getting there.
San Francisco is a city full of creative over-achievers. It's got a laid-back, live-and-let-live vibe that makes it very comfortable. People here like to play as hard as they work. One thing that I've found is that you'll make a ton of acquaintances but it's hard to make close friends, and that, to me, is really what is key to making a place feel like home. Cultivate your friendships early on and find people who know the city and can show you its many treasures.
Best of luck to you on this awesome adventure!