As Paul says, nothing in Europe can properly prepare you for the crack climbing and for this reason my strongest advice is to negotiate, beg, grovel, sell your soul or body (whichever gets the highest price) to make sure you have at least three weeks in Yosemite. Two weeks is unlikely to be long enough for a newcomer to The Valley with your skill level.
Secondly, do the same for your legs. This could be stair-climbing or step-ups. Again, below aerobic threshold, and lots of it, mind-numbing but effective.
.....learn how to poo in a bag