For me watering was a once a week sport. In very dry hot weather I'd kick the milk crates together to reduce evaporation but not much more than that. Peas/beans are reliable, productive and would be safe but would need a lattice of something to grow up. Lengths of string tied to the fence would do and be removable if you left the place.

Fun fact: beetroot leaves are delicious in salad when small and young. Can be cooked like spinach too. I sow beetroot pretty thickly and harvest most of them for leaves, only leaving a few well spaced out to make roots.