Everyone's going to appreciate the opportunity to wander a green garden in a t-shirt. Do it at night and you're getting a lot less radiation, and I'll wager it'll be a hell of a sky too.
My impression was that once you're down on the surface of Mars the radiation that isn't blocked by the atmosphere is mostly cosmic rays which don't depend on day or night.
So you're saying that beyond everything else Musk is also making contributions to the marketing of greenhouses? Because "living space" is always related to humans, as far as I can tell.
Though some other comments I think mentioned that it probably wouldn't be too dangerous to allow the occasional stroll through the greenery. Doesn't sound too far fetched if you consider I can choose to hang out at the park without a hat in exchange for an extra dose of UV radiation for the day. Not saying UV is on the same level as cosmic radiation, it's just something to think about :)