I fractured a rib almost 8 weeks ago (~very hard coughing!). I couldn't do any intense workouts for 3 weeks, but had no problem with easy, long runs putting in 90-110 mpw. I was aggressive the first week-- had a trainer at our university tape the whole side, and was getting e-stim and ice every day. The pain was completely gone after 3 1/2 week (although the knot took longer to go away), and I was able to start doing progression runs and eventually intervals. I'm getting ready to do my first marathon this weekend. My best advice is-- don't do anything intense until you stop feeling pain. How fast you heal is a matter of how healthy you are-- your diet, your sleep, age, your fitness, not stressing too much, not doing anything intense until you're healed.
I actually believe the light running helped me heal quicker-- they said it would take 6 weeks to heal, but I felt much, much better each week and with each run. Helps increase the blood flow to the area and keep the muscles from getting tight.