Korra's going to be very open about things like that. At least if someone asks her directly. She's probably not going to go around declaring herself the Avatar and she has a spirit of light inside her |D

Those days of proclaiming "I'm the Avatar and you've gotta deal with it" are over.

I guess the first move is having an encounter to begin with. Jason's been very open about his demigod status to most people or at least not shy about his powers and then when explaining them it comes up. So hopefully it won't be too tricky.