Saturday morning is the best time to go to Bonpland market. You can also take a whatsapp of the vendor on the left hand side past the first shop that sells variety of pantry products. His name is Enrique and you can message him Friday eve and ask to hold whatever it is you want for you, sometimes they ruin out of stuff fast if you are not there early. During the week they only bring stuff in once, and it stays there for the next day. Also fruit are sometimes not in a great shape, cause they are brought from Missiones / Salta, but veggies are usually fresh - tomatoes suffer some collateral damage. Mercado Punto Verde has very good quality and extremely fresh produce, but a bit pricier. A small natural almacen at the corner of Bonpland and Soler has produce brought in Wednesdays and Saturdays and usually has a huge variety of green leafy veggies, broccoli and some exotic stuff. It's a tiny place, but there are a couple of more stands inside - one sells dairy / meat products and the other grains and condiments and frozen empanadas etc. Those two are there any day.