This concept is so cool, and also is one of the most wonderful aspects of SE Asia. I've thought about it for years, but never had the guts to act on the fantasy.
By the way, I tried the People's Pierogi Collective combo plate (mushroom, potato, apple) at their Eastern Market cart. It was quite good. ----also at Mark's Carts.
If I were retiring from my current job (which I'm lucky to have), I very well might try to go open a place at Mark's Carts.
I've been a couple times now and I love it. But is it worth a long drive? That I don't know. Here are some highlights and lowlights:
The food has been very good to excellent with a wide variety of options.
I've had paella, pork confit sandwich, carnitas tacos, and whitefish salad. Typically there is a Spanish cart (paella), EAT (Pork confit and other sandwiches--my friend had their bulgogi beef with kimchi sandwich--she wanted more kimcheem but she is a spice head), a sausage guy (My next trip will be for his headcheese hoagie), a vegan cart (Haven't tried it yet), and Darcy's Cart (Carnitas and wfish salad, usually something like a breakfast burrito.) Just opened is an Asian bun cart (not my thing) and I hear pierogis are on the way.
It's fun to graze and eat outside. Lots of people watching at lunch.
I like supporting local business (most of whom use local suppliers) and the creativity is great.
Long waits for some carts, esp. at lunch, so this is not necessarily a quick option. Personally I am fine with waiting for good food, but I know some people find it frustrating. I suspect that the vendors will get more efficient with practice and seeing what dishes are practical for the venue.
Conversely, when I popped in around 2 the other day--there were only a couple of carts still open--everyone else had run out of food. So I think they are still working out some of the supply/demand bugs.
They are still constructing the seating courtyard so seating is limited. They did put up some shade sails which helps with the sun issue, but I bet they are broiling today--it was pretty fierce in the cart area on a day in the 80s.
I would say if you are in the AA area, check it out by all means!