If it is a dry year and there are no other water sources the antelope will likely still come in to the waterhole even with a recently constructed blind. I have had does and fawns practically drink as I was putting up a blind. Obviously if there are quite a few water sources the smart old timer bucks will water elsewhere. The antelope will obviously get acclimated to your blind more quickly if it blends in.
If you happen to hunt during rainy weather you will be screwed no matter how long your blind has been up! They will water out of puddles...although a few may still wander in to the waterholes.
I usually try to set my blinds up several weeks to a month in advance of the season so I don't have to dig a pit or camo them in. Some areas or states have regulations limiting blinds to day use, no pits, etc so be sure to check the regs! I usually hunt in Wyo where the wind usually blows 380 days a year and never have used portable blinds. I custom make my own and they have withstood the test of time. They are likely less prone to flapping, or being torn to shreads, by wind, cattle, and the elements!