From what I've seen, the Little Mermaid rooms seem to be in the same area as bldg 2, 50's, over at Pop is. So, having stayed in that bldg, I would say it took about 3 mins to get to the main bldg/food court/bus stops.
It took me about 8 minutes to get from the construction fence around the LM section to the main building. This includes stopping every 15 steps to take pictures in the Lion King courtyard. Without waiting to take pictures, I'd say it would have only taken half the time so about 4 minutes.