Should I?

I am thinking about doing a 10K on March 14th, just because it sounds like fun and my neighbor is doing it. Most of my running has been intervals on a treadmill and I have not been training to run six miles. Although, on my one adventure out into the cold, I did 3.5 miles with no problem. Is it too late to realistically do this "race"? The course is billed as being mostly downhill. Since it's sunny, I hope to take a run sometime today to get a feel for where I am at. I went skiing on Monday and I my right knee is a bit cranky with me because of it, so that will be a big factor in my decision. Registration doesn't close until the 13th, so I have some time to decide. What do you think? Should I do it or wait?