Do you have the gear? I am a complete fly fishing novice (was my second time ever) and went to Estes Park last September for a conference. We stopped in Kirk's fly shop and they suggested several flies to try. I went out wading in the river that runs through the city, including Estes Lake but didn't have luck in the lake. We did really well right outside the Estes Park Visitor center. I was learning as I went and still caught fish without a guide. I just found riffles, casted ahead of them and let the fly float through it. Caught several browns and rainbows and surprised myself. Had a blast.

Just wanted to throw that spot out if you didn't want to hire a guide. Literally right behind the Visitor center in an urban area. Lots of room to cast and not hook into trees on the shore.

Edit: Also visit the Patterson glassblowing studio if you're in Estes Park!