Places most newbies visit are:
Manitou Springs, Garden of the Gods, Palmer Lake, Woodland Park, Monument Lake. You can literally drive right up to the shore at Monument Lake and gangbangers from Colorado Springs like to go there and hang out in summer. It's never closed, but quite empty this time of year. There is also a hidden reservoir and pond a mile or so hike West of Palmer Lake. There's a large dirt parking lot with a rustic playground. You can drive right up to the trail head and be at water within 5-10 minutes, unseen, as the trail is enclosed by hills and trees. It is quite isolated in winter, and my boys were able to build a shelter off trail, which has been undisturbed for 2 years! Lots of people from Colorado Springs crowd that trail in Summer.