I don't know... I just can't imagine that he would do something like that right before one of the biggest tourneys of his life if he and his coach didn't think he could handle it without sacrificing his tennis at all.
It's NYC so I'm sure he'll find tennis courts like the ones in Houston to practice on and the SNL rehearsals are a whole week so I don't think it's all that terribly intense (unless he can't memorize his lines :P)
Plus, I don't think every one of the 8 will play on the first Monday in Houston, so maybe Andy will have a day off to get more used to Houston since he can't arrive til early Sunday morning (about a 3 - 3.5 hour flight from NY to Houston).
I'm sure it'll work out ok
And if Andy DID sacrifice his performance in Houston for a TV show then I guess we didn't know him as well as we thought. I can be wrong a lot but this time I really hope to be right lol.