Single Status Update
I emailed the San Antonio Parks Dept this morning and got this quick reply this afternoon.
This is state plane coordinats for the more expensive Survey grade GPS, not your less than hand helds.
The accuracy of the gps numbers are to the 1000 of an decimal inch, they geocachers would have to calculate it to what they use.
Coordinates for this spot for Geocaching is 29* 29’54.91” N
This beta conversion tool gets you pretty close.