Flight
Denver is the ideal airport to fly in to. There is a swift bus system direct from the Airport to Downtown Boulder. Check Google Maps for the bus times. Bus Lines, AB1, AB2 are the most common routes and the ticket one way is $9, Seniors get a discount. A Lyft/Uber from the Airport to Boulder runs about $50.
Hotel
This summary of options focuses on Boulder.
Hotel
Superior, Louisville and Longmont are just outside of Boulder and often cheaper. It's a very quick jaunt to get to Boulder from these locations. Broomfield is much further out.