If I ordered it from room service I call them when I'm done for tray pickup. All hotels and cruise lines request that you do this. It makes their jobs much easier and they recover the tableware much faster than having it go through housekeeping.
Your cabin attendant will have no problem handling it but they will really prefer if you have room service bus the dishes.
If I brought it down from the Lido then it goes back there when done. Bar glasses and such I leave for the room steward.
On a cruise I haven't had my tray left out for any extended period and I rarely see trays in the hallway and even when I do I can, even with my balance, avoid them.