It varies by resort. The first bus to DTD will generally be by around 8:30, at the latest. Service starts earlier those times of the year when TL opens at 9.
Service from DTD starts at 8 a.m., but direct service is limited to certain nearby resorts until 11 a.m. Travel to other resorts is available, but may be by an indirect route and take an hour or longer. Between 8 & 11 a.m., there should be a Transportation cm at Marketplace who will assist you in finding a bus to your destination resort. Regular service to all resorts from both MP & PI starts at 11.