Yep, you have to get into the park to get on the discovery trail. Taking jacobs crosscut from either end will add 2-3 miles to your trip, each way. I'm guessing your best bet is the trail from the minning camp resturant. I've never used it though. If you do use it, let me know how it went.
“Life is tough, but it’s tougher if you’re stupid”
John Wayne as Sergeant John M. Stryker, USMC in “The Sands of Iwo Jima”