No CSAs in New York? http://www.localharvest.org/csa/
Haven't read the Zone book lately, but as I recall it recommended getting no more than 25% of your carb intake from higher glycemic index sources.
Read, get most of your carbs from veggies. Problem - that is a lot of veggies since most of the lower glycemic index sources are also low in carb content since a lot of it is water and undigestable fiber.
My understanding is that most frozen fruits and veggies are flash frozen quickly after harvesting and thus retain their nutrients well. Issue is that if grown under industrial farming practices, the soil is typically artifically rich in the big three minerals N, P, K, but it is lacking in trace elements.
Ideally then, eat seasonally and organically while being mindful of glycemic load.
Non-ideally, manage your glycemic load (don't go crazy with high glycemic index foods simply beacuse you can get them in-season) and take a good multi-vitamin supplement.