For those interested, I was sent this by true-to-you.net regarding the Wolf Trap concert in Virginia:

Vienna, VA date, onsale and presale information

July 2 VIENNA, VA : Wolf Trap
Onsale 12 noon, April 14
Presale 10 a.m., April 12 - 10 p.m., April 13

For more details, please check http://www.true-to-you.net/