Michael -- to tell you the truth, I don't know when camp does officially begin, but as a result of purchasing a 10 game package, I got on an email list for upcoming events, etc and I just got the following which is an extract of the email:
Save the Date - Open Scrimmage
The Spurs will host an Open Scrimmage featuring the full team roster at the AT&T Center on Sunday, October 6. All Season Ticket Members are invited so mark your calendars. We will alert you via email as more details develop.
I started out with nothing and I have most of it left.