Re: Colorado in early April
You should have a good amount of water in striking distance, especially South Platte tailwaters. If you have flexibility, check what is fishing well closer to your arrival. Run-off can be hard to predict. You can call/check the websites of Angler's All, Trout's fly shop, and Blue Quill Anglers, all in the Denver Metro area to get an idea of how the rivers are fishing end of March and beginning of April. There are other good shops around as well as down in the Springs, those are three I check.
By the way, welcome!