Agua Caliente County Park is very isolated in The Anza-Borrego Desert. There's no direct way to it. You have to go over the mountains and then either north or south on the "Great Southern Overland Stage Route of 1849." That road name itself should evoke the Old West and the wildness of the area.
From San Diego you have to travel east 90 miles on I-15 to Ocotillo and then north for 30 miles (most miles, least time--2 hours). Or, you can travel 63 miles to the mountain tourist town of Julian and then down 12 miles to Scissors Crossing and south another 22 miles (20 miles shorter, 7 minutes longer (unless Julian is at its usually crowded and clogged weekend self--when it can take 20 minutes to get through the 1/2 mile long Main Street, which is also State Route 78 and 79)).
From Escondido, in the North County, it is 80-90 miles, and about 1 hour and 45 minutes. The shorter route goes through Julian, the less-trafficked route through Warner Springs.
Agua Caliente features a campground, hot springs and pools, and hiking trails. The birding is great in spring. That's when birds migrating out of Mexico at night find themselves at dawn over the great American Southwest deserts. Then the trees and water in this campground become a welcoming oasis in the dry surrounding lands.
As Marlene and I were about to depart from our lunch stop here, she spotted some movement on the hillside above the park entrance--our first views of Desert Bighorn Sheep (Ovis canadensis nelsonii)! Actually, the Bighorn Sheep here are quite distinctive and were formerly considered a separate subspecies called the Peninsular Bighorn Sheep (O.c. cremnobates).
Unlike other Bighorn Sheep, this variety is perfectly adapted to the desert. Apparently, their body temperature can safely fluctuate several degrees. This allows them to handle the cold nights and hot days of the desert during winter and summer. They are very adept at obtaining rainwater on rocks, and getting moisture from the plants they eat, so much so that they may not visit permanent water sources for weeks at a time.