Wow. I just checked this thread after a day, and I'm a bit surprised at the SF bashing. Personally I love San Francisco. I've travelled all over the world, and this is where I've chosen to live for the past 10 years. Yeah, there are better cities. But there's also a lot more worse ones.
Well, define sketchy? I'm hard to make nervous, and big white dudes who shave geometric designs into their beards seem to ward off sketchy folk...who'd have thought? It sounds good, and I love hole-in-the-wall type places. Is it the type of place where if you're not Indian/Pakistani you're given "the look"?
The Tenderloin is known for drug dealers, prostitutes, and cheap Indian and Vietnamese food. Personally, I've never had a problem in the Tenderloin. I wouldn't send my parents there, but a big white dude with geometric designs in his beard should fit right in with all the other hipsters getting curries. Fritz Leiber (author of the Fafhrd and Grey Mouser stories) and Dashiel Hammet both lived in this neighborhood back in the day.
You mentioned you like Indian food. SF is in the midst of a wave of new cheap Indian resturants opening, probably due to the fact that we've had a large number of Indian and Pakistani immigrants move here in the past 5 years or so. I've never gotten "the look".
Coming from Miami, you might be surprised at how many Asian resturants there are. Everything from Burmese to specific cantons in China are represented. And while it's not crab season, you might want to try the Dungenese crab. It's a real West Coast speciality. You can get it with the traditional seasonings down at the wharf (Alioto's if you feel like splurging), or Vietnamese style at PPQ (on Clement) or Crustecean (on Polk).
The Mission is only slightly sketchy, and has a very cool nightlife if you like divey bars, taquerias and trendy resturants. Valencia street between 16th and 22nd is a good place to start if you feel like exploring. You probably don't want to go east of Mission street, however.
One place I forgot to mention in my list:
Kate's Kitchen: Best Breakfast Ever. It's on Haight, near Fillmore; about 4 short blocks before Divisidero (and Gamescape). A mix of Southern and Californian cusine. My favorite is the Cinamon French Toast Orgy: big slices of French Toast smothered in granola, yogurt, honey, and fruit. Big enough for 2. The cornmeal pancakes with strawberries are also excellent.
Gamescape: it's fairly big, goes back kinda deep, and it's a bit cluttered. Hardwood floors that creak as you walk around. Contrary to what other people have said, the staff is very friendly, helpful, and knowledable. If they don't have something, they will order it for you. They have a great selection of RPG stuff and boardgames, and have an excellent selection of Go and Majong sets. In the back, they have a selection of used games and RPG material. Everyone has their favorite gamestore, I guess. This one's mine. I'm here about twice a month, just checking stuff out.
A last word of advice: don't rent a car. SF is a great walking city, in spite of (because of?) the hills. If you can't walk there, you can always take public tansportation (just don't expect it to be on time, however!) Parking in SF can be INSANE. SF was built pre-auto, so it really isn't laid out for cars. It's sorta like some European cities that way. From Union Square, you can take a bus or a train anywhere in SF or the Greater Bay Area. One of the great things about walking around SF is just happening on some garishly painted Victorian or some awesome view of the bay that rivals any postcard. You'll find the things that aren't listed in any guidebook.
Have fun!