It requires a lot of research and effort so may not be for everyone. What I have found through my research though is that you don't have to go religious with it and go 100% (which for most of us means giving up salt and coffee) for the whole year.
The best part is that you can do it say 80% so that you don't become an evil decaffeinated person like I surely would become. And you can do it for any amount that you can commit to (i.e. 30 days or once a week). So its not too radical, more an ideal way to live.
There are not only the health benefits to consider. When you source local ingredients, you are getting them at their peak. Ingredients that are flown have way across the planet must be picked immature and then ripen on the journey (loosing valuable time on the plant to gain extra nutrients). Then there is the environmental effects of all the extra energy required to transport these ingredients to your table.
The good thing about the research I did into it, is that I found out what is local to me and what is avail. in my region that I would have never knew about. I was really interested to find that there is so much avail. in Quebec but then it depends on the season. In the spring, which is when I first thought about doing this diet, there is almost nothing avail. So I think that I will wait to late summer/early fall to start so that I don't have to eat just meat and cheese. However there is a huge amount of things grown in green houses throughout the non ideal times of year so that you wont get scurvy in the winter.
Another thing that you can do is just choose local when you can. For instance, when I am in the grocery store and there are tomatoes from Quebec or tomatoes from Peru its a no brainer.
For more information or to see what ingredients are produced in your area check out...
100 Mile Diet