I'm 30 miles or so East of Ft Collins, but don't know of any groups specifically up there. However, I do know there is Two Rivers that rides around the Greeley/Loveland areas. I receive their weekly ride schedules and know that they ride all over Northern CO (including through the mountain passes to Estes Park) and have a nice women's group. The ride schedules, distances and speeds are too stressful for me, so I haven't joined them yet, but I have heard pretty good things about them.