The family is going to San Diego in January and I'm planning to run either the half or the full. I haven't signed up yet because I can't decide which. If I qualify on 29 Nov, then I'd just want to run the half. If I don't, then it would be nice to have a backup. Now if I don't qualify on the 29th, it seems unlikely I will on the course above, but if there's something crazy like snow or maybe I just have a bad day, it would be nice to have a backup.
I could run the half and then use the local George Washington birthday marathon (mid-Feb) as a backup but that race is notoriously cold and windy (and fairly hilly). Plus you have to run by yourself (most likely) while Carlsbad has a 3:15 pace group.
The B&A trail marathon is pancake flat, but it's in the beginning of March . I think Boston filled up in at the end of February this year, so this is out and mid-Feb might even be pushing it.
OK, I think I've just talked myself into signing up for the full at Carslbad! (And now I look at the website and you can transfer from full to half until January 4th! -- not sure this applies if the half fills though.)