Not sure if you're aware, but there's not much engineering in Littleton. Lockheed is really the only game in town. There's ULA in Centennial and a few others around in towns nearby. A few very small players.
As you mentioned - Colorado Springs jobs usually require security clearances because most work revolves around the Air Force Academy and their projects.
I'd suggest Boulder/Lafayette/Loveland/Longmont/Ft. Collins - Lots of big and small companies growing quickly. Aerospace, semiconductor, disk drives, software, consumer, etc, etc, etc. LOTS of work here. Startups, mid-size, mega corps, and academia. It's really turning into the second Bay Area, IMHO.
I've thought about renting out my driveway to an RV.