Re: Colorado in March?
I realize it is about 1-2 hours south of Estes, but I just returned from 5 days in Breckenridge and the surrounding areas near the I-70 corridor. Most major rivers (Blue, Eagle, etc.) in that area are flowing but with some ice accumulations in places. Even the smaller creeks have some open spots when otherwise iced over, but it has been a cold winter in the mountains this year so there is quite a bit of ice, especially on the smaller creeks.
The first significantly above freezing temperature (i.e. 40's) in months in Breckenridge was this past weekend, and it only lasted two days before the temperatures plunged back well below freezing. The worst problem will be stream access--the snowpack is about the 4th greatest since modern records were kept. You may need snowshoes or skis to access the rivers & creeks.
Mid-Febraury I fished the Blue River downstream (north) from Lake Dillon and had excellent results on #18 midges fished deep.