Bought a really laid back Heatwave heifer for a family I help back in the spring...she was haltered the first time in mid - late march, but not worked with a whole lot, we picked her up the 2nd week of April and took her to a jackpot the end of April, she probably could have gone as soon as she got home. They also have an Angus steer thats only been shown once, but they pulled the cows up at the in laws house, weaned him, vaccinated him, cut him, put a halter on him, and hauled him home all in one day...got home and he had the halter off, she stepped up in the trailer and put it back on him, he has led like a puppy dog from day one.
I think it all really depends on the calf and its individual attitude, there are some that regardles of how much you work them, according to some peoples standards they will never be ready to haul to a show. Then there are some that according to even the toughest critics standards are practically ready to haul the first time you put a haulter on them.
The one thing I always tell clients is it is very hard to simulate the show environment at home. No matter how much you work them at home or for how long or how well behaved they are. They are all likely to be spooky at that first couple shows.