I see these little yellow and black striped bugs every day on my cucumbers and I just squish them. Some of them are too quick for me and fly away:
The Organic Gardener's Handbook of Natural Insect and Disease Control says to use a pyrethrin spray or dust on both sides of the leaves - especially the new leaves - to get rid of them. I did this, but I still continue to see them. Not too many of them (yet), and thankfully, I planted a lot of cucumbers. They seem to be doing well.