Yeah, as others have said...I wouldn't worry about speed/cadence just yet....but to answer your question. I have a 40yo friend who just got into cycling and on his first few trips out, he averaged about 14-15mph maybe for 12 miles. The cool thing is that speed/endurance come quickly at first. We rode together earlier this week and after about 5 weeks, we did right at 40miles and I would guess his average was 17ish maybe? Granted he drafted a bit....I was impressed that at times he could keep up with us around 20mph for maybe a mile and then would drop back.

One of the best things you can do to improve speed is to ride with people faster than you. That will force you out of your comfort zone.