In March of this year, I was on a flight that landed at MCO around midnight. We boarded a ME bus around 20 minutes after landing. There were around ten of us on the bus and the driver waited about ten to fifteen minutes to see if more passengers would be boarding. None did, so we left. Luckily, we were staying at Riverside, which was the first stop. We got to the resort around 1:15am. (The bus driver drove very slowly!!!) That was my experience using ME at a very late hour. Nine pm could be different. The busses may be more crowded, so there may be a longer wait to board a bus. You can never tell though.