Too hot. Players lose focus quickly in that heat. That's why they moved to the Alamodome and then back to Oxnard. I agree with you on the artificial turf. Probably the main reason they still aren't in SA.
Their best years ever came after being in Austin for training camp. It wasn't too hot then.
Part of the reason they moved from there was the facilities were lacking. I was there back in 1992 before the 1st Jerry era Super Bowl. The crowds were really small which was good because they would have been overwhelmed with bigger crowds. I've seen middle school practice fields with bigger bleachers.
The Alamodome was much better in terms of accommodating large crowds but there's really only 1 field and it's the artificial surface. Moving the players between the Alamodome and the Hotel was a hassle.
The heat was even worst when the had TC in Wichita Falls.