'Very sorry to hear about that. Be really really diligent about the excersizing post-surgery. After doing the knee recovery thing myself a few years back, I'm really not kidding how important that is. I wasn't so diligent like a big weenie and it took me way too long to get back at it. Luckily, we're heading into the winter season and that'll make it easier to resist hopping on once the bike parts are in place!
Have fun in Moab.....there is nothing quite like it. If you are really looking for some punishment after a few days in Moab, go north an hour or so and try the 5MOH (Five Miles of Hell) trail in the San Rafael Swell. I guarantee that you have never ridden anything like it and it will make some of the Moab trails seem like child's play. If you want more info let me know at firstname.lastname@example.org. 5MOH is a trial riders paradise but a few of us sick individuals have ridden it on our "big bikes".