I've been working in downtown Los Angeles on a temporary basis for a few weeks and I've been going to the Grand Central Market for lunch quite often. I love it as a food court, but no one should ever make a special trip here. It is not a tourist attraction.
There are a number of authentic food stands, a few specialty booths, some produce and you can even get your eyebrows threaded. The food is very good. The prices are awesome. There is tons of character because it doesn't feel like a typical American market. It has a Mexican flair to it. Most everyone in it speaks Spanish.
I enjoy going there. It is simple, cheap and makes for good people watching. But I will never go there once my job ends. It's not even close to being like the Original Farmers Market in the Hollywood area. So, please don't mistake this for a tourist attraction. It isn't.