I'm 56, started commuting two years ago, and have been actively riding a road bike for a year. I do a wide variety of riding, from commutes to fast group rides, and I have just started racing a few weeks ago. Average speed has so much to do with your riding environment (how many stops; how much climbing) that comparisons are difficult, but here are my totals for February:

Count...................35
Distance..........564.49
Time.................35:40
Elevation Gain....12,949
Avg Speed...........15.8
Avg HR.................133
Avg Bike Cadence.....84

If I am just riding for an hour or so, with no training related goals or restrictions, my 'moving average' will be between 18 and 20 mph, at a cadence of 95-100. Cadence is both more important, and more comparable: RPM over MPH !!!!