In reply to Scrabble:
I'm firmly in the "do what your Dr says and give it time to heal" camp...
As others have said, it is a notoriously slow healing injury due to the low blood supply to the scaphoid. I had mine rebuilt with some bone from my forearm, a screw, and nine months in plaster + extra time in a brace and lots of physio. No problems as yet, only have a slight decrease in mobility (although initially there was talk of fusing the wrist), and no decrease in strength.
I don't mean this to be another horror story, more to make the point that a full recovery is certainly possible, however you will probably do very little for your chances if you try to get out on it too early.
My two-pennies worth is to avoid any loading of the hand (you'll never climb as well as you want to whilst in a cast, so why not just wait until it's fully healed and then get back on it, rather than damaging the wrist further and delaying the cast removal?) until your Dr gives you the OK. If you're really worried about work in August, then maybe start researching alternatives now?
Best wishes with your recovery.
Jay