I'd really like to know this too. I may be moving to Oahu for grad school in the summer! :) Also a n00b to the website as well as the lifestyle.
I think it's best to join a CSA. Ma'o has a reasonably priced organic program. If you explain your diet with them, they can probably work out a deal where you get more fruit than greens and veggies. If you're looking to buy in bulk on a regular basis, you should get in touch with the folks at Poamoho (http://poamoho-organic.com). They're really nice and they sell direct from their farm, so they might be able to cut you a deal. It's a lot easier on the big island....
Thanks Alicia! I cannot get into the Poamoho Organic website, do you have their number per chance? Thanks!
Prices are TOUGH here. I've found the most affordable produce here on the west side at a little Filipino wholesale shop called Jimmy's Wholesale Seafood and Produce (in Waipahu). UH Manoa has some produce sales around campus Tuesdays, Wednesdays, and Fridays. If you're in Honolulu, Kapiolani Community College has a big farmers market Saturday before 11am. There is also one at the same time on Kapahulu in Waikiki. Aloha!
Manoa and Waikiki Farmers Markets have the most local produce. The other ones cater more towards people wanting to eat plate lunches.