All that I do to prepare the veg/fruit for the juicer is wash it. I do not peel, chop, or core anything. The juicer that I have can handle things whole, so I don't have to. The whole thing takes me about 5 minutes to juice and then I immediately rinse the machine. I use water and a microfiber cloth (instead of soap), and then quickly dry it and put it back together.
Yes, it is noisy.
For our lunch veggies, we sometimes cut ahead of time and sometimes just chuck a cucumber and bell pepper into the bag and cut it at work (we have a kitchen in our offices; I brought an inexpensive knife for this purpose). But, usually we just chop it in the morning.