Stayed recently at Marriott Marquis Marina in San Diego for a tradeshow for a week. This is just to help others make a decision when going there. I cannot speak for all the rooms, but the rooms on my floor were as "unprivate" as you can imagine. You could hear people walking down the hall, showers being turned on in adjacent rooms, alarm clocks going off like there were in your own room, people talking in the next room, the constant train bells, and the conference room parties 2 floors down until midnight. It was extremely painful.
FYI - I was placed in the South Tower - facing the street on the 5th floor. Needless to say - if you stay in this hotel, make sure it is HIGH in the towers and facing the marina.
Last thing - for consideration:
The in-room wireless is a MASSIVE rip off. You now have to pay $12.95 per DEVICE. If you have a smart phone, PC and iPad - yup - thats a whopping $39/day. You can't even bring your own wireless router for the room - somehow they figured this out too.