If you’ve been dragging your feet about finally signing up for the Air Force Marathon, you might want to make a decision fast. Not only is the time to sign up before a price increase goes into effect approaching, but marathon officials are predicting that the event might be sold out before it does. On April 2, the cost of the full and half marathons increase to $90 and $75, respectively. The 10K will go up to $45, while the 5K will remain at $25. The prices go up further on June 2, but that’s only if there are any…