Just got back from Lima (first week Dec 2015). Callao is under emergency, our tour guide told us when sending us to the airport. Callao is a bit run down, so at any time, never go alone. Seemed busy tho but it is a notorious area.

Miraflores, Barranco is fine....all pleasant to walk about. Friend and I walked at sunset from Barranco back to Miraflores by the sea (and parts were not always lit). Nothing happened, just taxis beeping us to take a ride. We ended at La Rosa Nautica for a quick drink. It did cross my mind about safety but Miraflores seems ok

Best arrange a hotel taxi to Airport and back, or Uber it. As taxis are not price controlled or metered, i found Uber useful. Get a local SIM for internet/calls (esp Uber)...Claro at Ave Larco has some staff that can help.