I know it can take weeks to acclimatise to higher altitudes - it really does depend on the person, there is no hard and fast rule, however, altitude sickness can kick in after 12 to 48 hours, I think the last thing we need is to have one of our guys sidelined with this, they wouldn't be able to suit up and play.
Denver is at 5,500' Colorado Springs at 6,320' Mexico city around 7,000'.
Also, giving the players a gradual increase in altitude reduces the risk of altitudes sickness occurring, but if it does it gives the players time to get over it. Another thing they may be trying also is increasing their intake of iron rich foods to boost the iron content in their blood to take on board more oxygen - I know this is a trick used by high altitude runners and something I used to do before going skiing or climbing the highest I've been is around 15,500' and I can't remember any effects of altitude sickness, but like I said at the start every person is different.
The argument about driving within a day of playing I guess doesn't give you time to acclimatise to the altitude but means you may miss the altitude sickness before it kicks in.
I'm not a professional when it comes to these things by far, but I sure hope everyone, especially the big guys have their own personal oxygen tanks with them!