there is a new service to and from Denver airport to Longmont called GREENRIDE. Nice new vehicles and courteous driver when I took it. Reasonable price.
IT will cost alot. Honestly your best bet is to look for a bus called AB1 it takes you too Boulder station then take the Bolt too Longmont and get off at 287 and Ken Pratt and it's only a block or so south on 287. Hope it helps
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