How far do you stay from Mongkok MTR Station? If you get clost to it, you can go Mongkok- Lai King- Sunny Bay-Disneyland. It takes about 32 minutes, costs 18.5HKD. This will be faster.

If you want to take bus: take bus E21 at those bus stops (Fife Street, Reclamation Street/Bute Street, Nathan Road /Prince Edward Station, Nathan Road) to Lantau Link Toll Plaza, then change to bus R8 to Disneyland. Bus fare: 14 7HKD. Buses are available every 10-20 minutes till midnight.