According to the d23 website the summer issue was available in the parks:
You can read these stories in the summer issue of Disney twenty-three, available to D23 members and at Barnes & Noble booksellers, all domestic Disney Stores, Disneyshopping.com and at Disneyland and Walt Disney World. Back issues will be available at Disneyshopping.com.
The last two issues are available at Disneyshopping.com for $15.95. These issues don't come with the little gifts, or at least they haven't in the past.