Linda,
Here is a link to the Earthbox forum:
http://forum.earthbox.com/index.phpThis will tell you a lot about it, and also you can see how many people grow in JUST earthboxes, due to bad soil, etc. Click on the "Store", and it will tell you about how the things work, though you don't have to buy their "soil", as it is easy to mix up (though, as with anything like this, everyone has different formulas!). The basic formula is to mix up about 70% peat with 25% vermiculite and 5% perlite, and for one of the 2 cu. ft. containers (approx 15 gal) add one cup dolomite, or two cups for tomatoes (something they need to prevent BER), then make a 2 ft trench on one side or the middle, depending on what you are growing, and add 2 c of a basic 10-10-10 granular fertilizer, covering it with more of the mix. This slowly leaches out into the medium as the season goes on, fertilizing constantly, but slowly. There are all sorts of tricks I learned my first year with them, like adding a tsp. of calcium nitrate to the watering tube weekly, for extra N and Ca - supposedly only done for tomatoes, but I did it in all of them, and something must have been done right. I also add things from my hydroponics, since I'm sure that can't hurt!
One good thing about this is that the growing medium is used for multiple seasons, as the peat does not break down. The fertilizer strip is dug out, and a new batch is added the next season (I just added it to my garden). I found a trick on the forum to make this easier in which somebody uses "brewing socks" to put the fertilizer in, and this can just be lifted out.
For watering these things, I do it the way I do the rest of my garden - with drip emitters on timers! I tweaked the amounts by adding a 2 gal/hr plus a 1/2 gal/hr to one, while just a 2 gal/hr on another, which uses less water. Then, as it gets hotter, I increase the time, as needed. There is an automatic watering system they sell for it, but I've read about too many problems people have had with it.
Good luck if you decide to try it!