I'm not worried at all. I don't think this info is reliable. If as many people were really at Woodstock as now claim to be, the event would have taken up the entire state of TX. The defense better be careful how many people they try to throw in there, too, because I don't imagine too many people could have been in that specific area without tripping over each other.
There are several reliable witnesses, documented to be in that area, who have stated the area was underwater. There should also be piles of forensics, plant life, etc., to verify the area was underwater.
IMO, it's also going to take a lot more than a few people saying the area was dry to overcome Casey adamantly insisting Caylee was left in the care of a nanny, (nanny's sister, nieces, and mother, another child watched by nanny, that child's father, and a few friends,) all of whom NO ONE, including the defense, can even prove exist.