There are two options to travel to Boulder from Denver International Airport
Ride Share (Uber/Lyft)- approximately 40 minutes $90-120.
RTD Bus - 35 minute travel time. Buses usually leave once every hour from the airport terminal to the Boulder Transit Center (two blocks from the St Julien). Fare is $10-12 one way. Bus drivers will load/unload your luggage.
Bus Schedule Link