Jump on the Queens bound F train when you're in Manhattan, and take it on down about two stops past Roosevelt Island. Once you're there, exit from the side where they have the giant double glass doors. It's a short skip and a jump away from there, at the end of 35th, with a hideous like peach and pink (? not 100% sure) awning over it. You'll see lots of the produce sitting outside. Meanwhile, Subzi Mandi is such an iconic place that literally anyone on the streets can tell you how to get there.
Pros: Excellent produce, full selection of spices, full selection of snacks, extremely competitive prices, extremely fast staff (when checking out), helpful people all around you
Cons: staff isn't exactly very helpful