If your knowledge of Spanish is nil, good luck. Unless you hit the ultra-touristy areas (and there aren't many in Madrid) you'll be screwed. Madrid isn't a tourist destination in the same way as Barcelona or Seville.
Obvious locations are Palacio Real, Plaza del Santa Ana and surrounds for nightlife, Parque del Buen Retiro, the botanical gardens and Monte de El Pardo. Barajas Airport is a phenomenal piece of architecture, too, but for €6billion you'd hope so.
Security-wise, it's a capital city, so treat it as such. Don't be an idiot, and keep people at a distance and keep your wits about you. Anyone that's deliberately within two feet of you should be regarded as a threat. Try not to look like a soft target. Rules to deter personal crime are the same as those in any other town or city. Be purposeful, don't behave like a tourist, and stay aware.
That said, I happily wandered around with my D80 Gotcha'd to my wrist, as I did in Barcelona, which carries much higher risk. The only time we came close to crime was when we were offered some weed in Retiro.