The idea of self-sufficient life skills has always been of interest to me. So much so that I do it for lengths of time such as a week on the Appalachian Trail (next trip possibly 2 weeks this June). So to that end, I encourage your pursuit.
I looked at the website and I'm still not clear how getting locally grown food is of benefit. Is it just the idea of eating fresh produce and supporting local farmers?
Totally. Also, knowing and meeting farmers is a community building act, as is the group itself. If you get to know the food producers themselves, better food choices can be made. This is the magic of farm folk, who I've spent a lot of time with already with both the SO and I being first generation city kids - when you have a relationship with the person who grew/raised the food, you get the inside track: the red peppers are nice and sweet this year, the cabbage has some sort of blight and isn't keeping well, this chickens only good for stewing... etc. They also argue that food safety is less of a concern (not sure if I believe this, unless you grow it yourself, there's no way of really knowing. Is a larger farm more or less likely to maintain safety standards? I don't know.) The linked sites also talk about a reduced ecological footprint, as purchasing more locally reduces transportation of goods and related pollution.
Also, Ash, I must agree with linnea - what world do you live in where there is too much tomato anything? Isn't the idea of canning that it'll keep til it's needed? Or am I wrong?
(edit: also, there is a theory that it is healthiest to eat food native to where your ancestors are from. Mine are from right where I lived, hence another benifit)