Okie dokie. Here's my professional take:
First of all, a question: what did you break and how many bones? Bimalleolar? Trimalleolar? Any pins/plates? Do you know if they had to fuse any part of your foot or ankle?
That will change my answer ever so slightly, but not too much.
As for trail runners - depending on the specifics of your fracture, I wouldn't fret about it. I would actually encourage you to use running shoes before boots. If you wear higher cut boots it actually changes the way your ankle works, and not necessarily in a good way. And honestly, if something bad is going to happen to your foot or ankle the boot is NOT going to stop it. The higher, stiffer top is high and stiff enough to stop your leg from translating over your foot properly, but not high and stiff enough to prevent any sprains or breaks.
Don't worry too much about telling your PT about getting out BACKPACKING. Just say you want to get back to trail running and that you need a great deal of balance, agility, and proprioceptive training. Make sure they are doing joint mobilizations on you...if not, let me know and ill try to find you a new PT who will. If you've had surgery, or been in a boot for any length of time, your foot and ankle are going to be a bit of an immobile brick. Simply stretching the muscles isn't going to cut it...the joint capsules themselves are scarred and fibrotic and will need to be stretched individually...something you cannot do yourself.
Your attitude of thinking your rehab is going to take a while is a good one - but honestly, if you are in pretty good shape and are diligent about your exercises, it won't be as long as you think before you can get back out on the trail. You won't necessarily be the fastest or surest footed out there, but it shouldn't be too long before you can strap a lightweight pack on your back and hit the trails. For your first trip you may want to consider one of those old-school looking lace up braces. Don't use it a lot, but for your first trip it might not be a bad idea. You might not need it at all...just see how you feel.
Feel free to email me with any questions...I'm always happy to help. I do my best to battle all the bad medicine - including PT - that's floating out there all too frequently.
And that offer actually goes to anyone who has questions about any of this kind of thing...as several of you have mentioned the medical system doesn't always have good answers, so if I can help you wade thorough some of the crap I'm more than happy to help if I can.
jenmitol AT gmail DOT com