I used to subscribe to a CSA (community supported agriculture) box before I moved abroad, and I actually found that my grocery spending decreased. This was pre-MMM and I definitely was one of those folks who would go to the grocery store with a list of three things and come out with ten. So - avoiding a trip by getting a CSA actually really helped me, plus it was fun, and beautiful produce!
Is that an option for you? I'm all about spending money locally whenever possible, and it sounds like the health benefit alone makes it worth the cost for you.
I second the CSA! Do you live in an area where this is available, even for part of the year? I'm on the west coast so we get one year round. 20$ a week for beautiful organic produce, usually 8-10 items. Our friends routinely compliment the taste of our veggies (lettuce is crisper and sweeter, etc.). It can be challenging to a) come up with recipes for the things we've never had before (but that is part of the fun), and b) to eat it all before the next batch arrives (harder in the winter, when there are tons of root veggies and leafy greens).
If that is not an option, here are 2 ways to reduce your spending:
1) Visit the farmer's market late in the day, when farmers are ready to wheel and deal to get rid of their produce.
2) Buy multiple products from one vendor. They will often give you a discount if you are buying a bunch of stuff.
3) Buy from the same people over and over again. They will get to know you and give you deals.
4) Consider getting a job selling at the market for one of the vendors. I have a number of friends who have given up their sat or sun mornings to do this. For them it's not about the pay, it's about getting to know the other vendors, because they all trade products at the end of the day, and so they take home tons of produce.