In reply to rob sykes:
Hi there man....I know it does not help, but you have all my sympathy...
First of all, I am no MD, so my input has not the intention to function as a medical advise, whatsoever....but I have been there, and I remember that it cheered me up quite a bit when ukc folks answered my post with their own experiences.
I broke my Talus on early December 2011 at Arco...did not need surgery, however my plaster time was a little longer (75 days)I still rememmber thos freaking injections on my belly...f**k.
What I understood from my ordeal was that that least you have to worry about is fracturing the same spot again...The main issues in that area will be "arterial/venous suffering" since it is a less vascularized area and it takes much longer to get back to "normal". And the other issue would be an eventual post-traumatic arthritis, which I believe in your case is still early even for MD'S to tell for sure.
My first activity was hillwalking around April and although it would get huge and quite painfull after a 3/4-hour walk (ice and rest for a few days before going to another walk), it visibly improved, especialy the stiffness. By June I was going for strolls around the Breithorn area and it was still hurting on the way down. By June I also started climbing on the bouldering wall.
Now it feels like almost 100% even though I haven't had any busy multi-day trips so as to fully evaluate my situation.
Although I do not think you would have problems bouldering, be aware that psychologically it has affected me even while leading even on easy sport routes, so it may affect your willingness to take a fall while bouldering, which IMHO can hurt you ability to fall unharmfully. But who knows man.
I hope I was of any help, even though I insist that nothing substitutes a competent and interested MD, who is also willing to look at your case as an individual one and not as just another number in a mass production system(which was not that easy to find in my whereabouts).
p.s.- altitude bouldering may help your cardio, but it will be the same for the injury as sea-level bouldering
Cheers