SanMarco area is always very noisy and crowded, with apartments, stores, shops, eateries, bars all crammed in like sardines. Nonstop din of chatter, partying, clinging and clanging of dishes, kitchen pans, cutlery and silverware. I'd suggest staying someplace across the Grand Canal- on the other side- and you'd still be very close to all you might want to see.
Oh yes, you won't find a tree growing anywhere here; it's all limestone, concrete, canals, and walls, until you leave for the outlying islands. I did notice some greenery (weeds actually) growing from a few cracks in the outside steps of some of the very many churches in the area.