Regarding your question about the garden layout, I think going with raised beds along the south fence would give you the best sunlight through the day. The soil there drains well after rain and you won't have to worry about the walnut tree roots interfering. I would suggest mixing in some compost about three weeks before planting so the nutrients settle. For tomatoes, you might want to put cages in early so the branches don't sprawl. Basil and marigolds around the edges help keep pests away naturally. If you decide to add cucumbers, give them a trellis so they climb instead of taking over the ground space. Watering in the early morning works best to reduce evaporation and keep the leaves dry. I can help you set up a simple drip system if you want. Just let me know when you plan to start and I can bring over some extra starter plants I started from seed last month. They are small but healthy and should transplant well.