Before sending actual people to a far away place like this, it'd be nice to experiment if plants could actually grow in sterile and probably very poor soil. It would also be a good time to demo the machinery and AI of worker robots.
I assume you couldn't grow bare root seedlings, but that the plants would need to come with some minimal starter soil.
A martian experimental miniature greenhouse wouldn't have optimal heating (passive solar heat, possibly some additional heat from radioactive battery) and the crops would have to be rugged and cold tolerant.
Taking some hints from modern day eskimos here are some candidate crops:
wheat, barley, kale, cabbage, potatoes, onions, spinach, rhubarb, beets
Could a robotic agricultural station manage to grow anything at all, and if so, how much, and how much would it cost to put such a thing on martian soil?
Secondly, do we have any idea of areas where the soil is more tolerable?
Too near the basins the soils probably have been too exposed by the salty brine.
There are also other problematic chemicals known to exist in martian soils:
http://www.slate.com/articles/technology/future_tense/2015/04/perchlorate_in_martian_soil_the_chemical_that_could_be_dangerous_to_astronauts.html
https://en.wikipedia.org/wiki/Sodium_perchlorate