Actually, the cabins on the Lido deck are near the front elevators on the Grand, not the mid-ship elevators. They do not get as much action as the mid-ship or rear elevators (due to Horizon Court/Skywalkers, etc being aft). Only people who actually have cabins in the forward section of the ship are likely to use these elvators. That being said, you will have a bit of traffic. But, I've never heard anybody in the Grand Suite (which is adjacent to your cabin) complain about this, so I don't think you'll find that a problem. Also remember that the Fun Zone is right above your cabin, so it may not be quiet in mid-day.
My sister was in L254 on our first cruise. I found it very incovenient to have to walk the entire length of the ship, through the pool areas, to get to Horizon Court. I almost slipped a few times on the slippery deck. When it's crowded it's a pain in the butt. But, many people love this location due to it's close proximity to the pools. We really don't do the pools, so this wasn't important to us.
I would not consider it an upgrade if you already had a balcony cabin (BC or BB) on Caribe (since the balconies are larger). I'm not sure why the balconies on Lido are BA as their forward position and being on the highest deck with cabins, I would think would make them less desirable.