Broadway has got to be the absolute worst route through town. There must be a hundred ways better than that. I would also avoid 28th street south of Jay.
From South Boulder Road and Cherryvale, my choice would be the following:
Cherryvale Road north to Baseline (the Baseline that goes East). Turn left and then take the bike path north, under Arapahoe (after a few blocks on Old Tail Road), past the Stazio ballfields, under 55th, under Pearl, through Valmont Park, under Valmont, west to 47th Street, north to Jay, west to 28th/US36, and north to Lyons.
http://toporoute.com/cgi-bin/bicycl...calls=setNormalView,clearMetric,setFollowRoad
I do this all the time. This is roughly the same route that dteuscher recommended.