Hi there, I'm just down the hill in Longmont. I don't have a lot of experience with the park itself (we have dogs and like to take them with us - no dogs in the park). You could ride down and then back up several canyons (36 and 7 go into Lyons, I would recommend 7, less traffic and prettier, 34 goes into Loveland, I've only driven this a couple of times, not sure how it'd be on the bike). A great ride would be to head out of Estes on 7 toward Hwy 72 aka the Peak to Peak Hwy which goes to Nederland, a funky mountain town at the top of Boulder Canyon. While there are lots of ups and downs, you stay at relatively the same elevation, as opposed to dropping the 2,500 - 3,000 ft down to the front range. The views along the peak to peak are fabulous, its a designated scenic route. Just remember to drink a ton of water, its "high and dry" here. Oh, and I just have to throw in that we got married in Estes Park, at Lily Lake which is technically in the park, but just off Hwy 7 outside the entrances. Have a great trip!