YC bus is shared with the BC.
Sometimes with the Swan/Dolphin. & BW - depends on time of day and how full the bus is.
Bus to AK & MK - both would take between 30 and 40 minutes.
So if you wanted to be at the park at 8:15 AM - then stand by the bus stop by 7:05 AM and wait. The bus may take 20 minutes to get to the resort.
We always leave 1 hour to go from resort to park.
Even for the boat to DHS & EPCOT. You may wait at the boat daock for 20 minutes - then YC to EPCOT is about 15 minutes and YC to DHS is about 25 minutes.
good luck.