I was just at ASMu for a spontaneous 1 night trip this week. I do not normally use the buses, but decided to try. It was 7pm, MK closed at 8pm and I wanted to catch Wishes. Was the bus right there when I was done checking in? YUP. Got to MK lickety-split.
Then I took the monorail to Epcot for EMH, and at 11pm, the end of the evening, walked to the buses.. Was AsMu bus there? YUP. No line, we waited maybe 5-10min. more for other people, we all had seats, and then we were off to the resort, no other stops.
As someone mentioned to you, you are going at a busier time, so there will be more people, but I was BEYOND DELIGHTED with how fast and convenient the buses were for my little, mini-trip.