I know I state that I am a new runner, but I am new in the sense that it has recently become a big part of my life. I have run for years, but only here and there. I finished my senior season as a college football offensive lineman about 7 months ago, and I am down about 50 lbs. I have never run a half marathon before, but I will be running one next Sunday and I am more than confident I can finish. I ran 8 miles the other day and did not find it difficult, and I can keep a 4 mile split of 7 minutes. I think I am in good shape for a 220 lbs guy and I am pretty athletic.
However! I really want to run a marathon. It is something that is very important for me to achieve. I know I have the willpower to train and perform at that level, but I am not sure how long it will take me to prepare for that. I only started running a month ago to get to where I am at now. My question is, could I be ready to run a marathon on October 5, 2014? I really want to participate in the Portland marathon, but I don't want to register if I cannot handle it yet.
You can finish a Marathon, no doubt about that. I think that you should go slow. Don't rush, you will risk getting yourself injured. You don't want that. Start out with a half marathon or two. The Marathon distance is much harder.
If I were you, I would wait until at least next year, to run the Marathon distance, to ensure that your body is fit for it. When you are able to run 20 miles and have done so for a couple of workouts, you are ready for the Marathon.
I cannot second jesperg's "run a few half marathons and wait a year for a full" suggestion enough. Running a full marathon without at least 1,000 miles under your belt in the previous six months is a recipe for injury.
We may be forgetting that SeanDalton may already be very athletically fit... but I do agree with shippo and jesperg that a solid base of running is necessary for marathon training.
On the other hand, be conscious of the fact that you have a bare 10 weeks or so before your marathon... Assuming that you've been building a base for the prior 8 weeks or so, you are on the dry side of being ready to run 26.2 miles. If you are going to go for it, get your long runs in (20 miler's - try to get two of them into your schedule), and make sure that you taper for the last two weeks. Most importantly, arrive healthy and injury free at the starting line.
Another thought for you: in consideration of the training effort and investment of your time, consider running a marathon either later in the fall/winter or even that same marathon next year. Train for it with vigor and have fun running it. There is nothing worse that having a crappy marathon.