Ooh, that sounds like a really good size and situation - you can grow a lot of veg in an area that size and handwatering it with a decent sized watering can is eminantly doable if necessary (especially if you don't have stupidly hot summers the way some of us do).

So, my other advice at this stage is to be aware of what plants are going to be permenant - like lavender and any of the woody herbs like sage and rosemary - and decide on their placement first because everything else you can move around from season to season if they don't work in a particular spot. I don't know if you have access on all sides or if one side is up against a wall. In the first case the general rule would be to plant the taller plants in the middle (like tomatoes) and the shorter ones around the outside, in the second case the same thing but taller at the back.

My last piece of advice for this morning is that as gardeners we kill a bunch of plants in learning how to garden so don't worry if some of the things you try don't work. Just plunk a different plant there and see what happens.

Looking forward to hearing how it goes; feel free to hit me up for more advice :)