I've been reading a lot of Local Food blogs and discussions, and have been thinking about this issue.
First of all - I have always been a supporter of local, fresh, seasonal food. I won't eat asparagus in November - that's just silly. That's time for broccoli and brussels sprouts. On the other hand, I eat frozen peas all year. Their season is so short, it is often hard to get good fresh ones even in season, and the frozen ones are good and work into so many dishes so well. (Rich calls them "The default vegetable.")
I have shopped at Greenmarket since it opened, even sometimes when I lived in New Jersey. I was also involved in the early stages of a farmer's market there. The food is wonderful. Five months of the year, though, there are almost no vegetables. Our farmers come mostly from New York State, and the first greens really just started coming in at the end of April. Also, they are not less expensive than the grocery stores, but frequently more so (for much better quality and freshness, of course.) I frequently see people in other parts of the country happily talk about saving money by buying from the farmers, but that just doesn't happen here, and our budget is a major consideration.
We are fortunate to have many things besides vegetables. Meat, dairy, even fresh fish (about a third of my locavore circle is water) are all available. I can even get some grains! We'll be eating local polenta tonight.
We also just joined a CSA. I'll see how that goes - it is less forthcoming than some with information and "customer service" stuff, but it's also the one within reasonable walking distance, and it has half shares (and even, I gather, a winter program.)
I have other considerations, though. The budget, as I mentioned, is an issue. For various reasons, I prefer that a substantial amount of our protein come from vegetable, rather than animal, sources, though we are by no means vegetarian. I have not seen any local sources of beans, though - I don' t think they are really the most sensible use of farm land in this area, and they do ship well and inexpensively. When I buy my lentils at the natural food market, I don't know where they come from, and it is not my main concern. And I can't eat much cow's milk - the soymilk I use is definitely not local! (Though when I can make my own soymilk, I think importing the beans from a family farm in the Midwest, but making it here, is quite reasonable.)
All this musing is to decide if I want to join One Local Summer. That is not all local, all the time, of course - the concept is that you prepare one meal a week from exclusively local food. (Oil and spices, I think, are the usual exceptions.) To me, it feels a little artificial - but, at the same time, an interesting challenge. If I do, I may make my locavore circle 150 miles. Too much of a 100 mile circle from here is either city/suburb or water. (I consider anyone at Greenmarket to be local - I'm not going to go plotting them on maps, and rejecting someone who travels to make this work!)