If you leave now, you can be putting in at Shoshone this morning. Just scout it to make sure there are no ice dams.
The main boating season in Colorado starts when you decide that its not too cold to boat. A maxim to bear in mind that'll greatly add to your enjoyment of your new home is "There's no such thing as too cold, just under-dressed." The rivers typically will start flowing in April and May, peak in late May/Early June, and then subside. Dam releases will keep some rivers flowing through the summer.
Take your copy of CRC2 and spend some time checking out this site
you can plot custom hydrographs of various gauges throughout the state pretty easily. There's also a link to flow sites via this website and the AWWA site.
Go to the MB party tonight to meet folks too!