For the closest night out of Mission Viejo, drive up the canyon to O'Neill Regional Park, where coast live oak and sycamore shade the seasonal Trabuco and Hickey creeks and the trails climb into chaparral toward Saddleback. You hike or ride the canyon by day and sleep at Arroyo Campground, the park's run of gravel pads with no hookups. That is the catch. There is no power at the sites, so a generator between 8 a.m. and 8 p.m. is your only window for air conditioning, and the rest of the night is dry. This is inland Saddleback, hot all summer, not the marine layer down at the coast. The creeks are seasonal and closed to wading, so it is trail-and-saddle country, not a swimming hole.
The canyon climbs to Vista Point at 1,492 feet, a clear-day look out toward Catalina and Palos Verdes. Farther up Trabuco Creek, Holy Jim Falls is a shaded 2.8-mile walk through old bee-tree country, but the road to the trailhead is rough dirt that wants four-wheel drive, so leave the van at the park and go up in something else. Check Cleveland National Forest alerts before you count on it, since the canyon has sat under a burned-area closure.
Arroyo Campground and the canyon rules
Arroyo has 79 individual sites, each with a gravel pad, a picnic table, a fire ring, and an elevated barbecue, plus community water and three restrooms with hot showers. There is no park-wide RV length limit posted, so pick a site on the reservation that fits the van. For more room than a campervan gives, larger RV rentals across California size up from here.
If Arroyo is booked out, Caspers Wilderness Park on Ortega Highway is O'Neill's OC Parks sibling and the nearest overflow, on the same combined 14-night limit per 30 days. Bring firewood already certified pest-free, keep flames in the rings and barbecues, and plan the generator run around the heat, because inland weekends here can stack an extreme-heat warning and a red-flag day together.
Down to the Orange County coast
The beaches are the other Orange County trip, and neighboring landers lead them. For San Onofre, Doheny, and San Clemente State Beach, the San Clemente campervan page has the pads and the walk-ins. For Crystal Cove and the Newport coast, Costa Mesa is the base. More bases up and down the state sit on the California campervan hub.