A great source of information regarding the Training Facility located in the California desert was written by Francis Blake, Dwain Oliver and Lt. Col. John Shaw Lynch for issue #132 of the British magazine "After the Battle". We don't have a copy of the article but you can get ordering information at After The Battle's website - www.afterthebattle.com.
In the article, the 6th Tank Destroyer Group as well as other TD Units are listed as having trained at the center, the HQ of which was located 26 miles east of Indio, California. The center itself was stretched over a broad expanse of desert in southeastern California and western Arizona. The Camp Young and Camp Ibis shown in the unit's payroll records were areas the unit bivouacked. The size of the training area was larger than England. The Group trained under Major General Charles H. White's IX Corps.
The photo shows Major General George S. Patton reviewing a demonstration of a tactical problem at Camp Young training area, Desert Training Center, Indio California, 6/4/42. Photo from the George S. Patton Museum.
Additional sources of information about the Desert Training Center:
3.) Article by La Posta Publications which is really about the Postal History of the area but it includes much information about the training area. On the last page of the article it lists the 6th TD Group as being stationed at Camp Young from 1/8/43 to 7/31/43.