I've been running for a couple years now.  Done a few half marathons and do a 10-mile run every weekend. Did a 16-miler last weekend.  Knee was pretty sore so I thought adding that extra 6 miles may have been pushing it.

Would like to attempt a full marathon and wondering if I have any business even considering it.  My best bet is the local one in 2-months time...or I end up having to travel for one in spring or waiting another year.  People that have been there, done that, is 2-months a realistic period of time to prepare given my current fitness level?

I wouldn't go into it "blind" (i.e. without completing at least one close to full distance training run).  One really needs to put in the "big" miles in order to know with any kind of certainty that one could complete a full marathon, especially with your knee problem.

By big miles, I mean a lot of 20+ milers and it's difficult to do very many long runs in the time you have left without over training.  Since you aren't looking for speed you could drop any/all speed work and just focus on getting a couple/few long runs in per week in the time you have remaining.  You are threading a needle between getting enough miles in and not aggravating your knee in training.

One would think that one could just slow down and run a lot longer but that doesn't work for me; essentially you are still running at a pace at which you haven't trained and for a lot longer time than are used to.

I had run quite a few 1/2s prior to my first full and thought it would be easy to ease off the pace and do a full:  wrong.  I remember thinking even if I way more than doubled my ½ time I'd still come in somewhere just over 3.5 hours; reality was at 24 miles I started thinking I might not finish and made it just under 4 hours (3:52).

It sounds like, barring knee problems at the longer distance, you are within striking distance.  It comes down to how well you want to do and how painful you want to make it:  go for a "finish at all costs" this year or put in the miles and have fun next year.

Thanks,
I decided not to push it and will attempt a marathon in spring.  I have a 1/2 in a month and then I'll start slow with a 26-week training schedule.

I think youre making the right choice.  Theres no way you could hit the distance you need to realistically without running into a ton of injuries.