The Preserve is managed by the Bureau of Land Management, including 147 acres that are managed under a cooperative agreement with San Bernardino County, to protect rare and endangered wildlife, enhance sensitive riparian zones, promote the growth and restoration of a wide variety of plants, and offer educational opportunities. There are numerous trails to walk and hike, including a wheelchair-accessible boardwalk through the marsh and riparian habitats.
Big Morongo Canyon Preserve was a great place to stretch our legs, look for birds, and do a little education on desert ecosystems. I recently visited with my two kids (4 and 10 months). We enjoyed the Marsh Trail (a boardwalk) that goes through the marsh area under the shade of the trees. There were several trails, we chose to stay within about a mile from the car, but it would have been possible to continue hiking into the canyon for several miles. We saw quite a few bird species, lizards, and were shocked at the amount of water considering we visited during a drought. The hiking that we did was easy for my 4 year old. The preserve offered bird watching guided walks as well but we were not visiting at the right time for a walk.
The parking lot was shaded and the bathrooms were flush toilets and clean. There were no dogs allowed on the property (although we saw a few locals with their dogs weave onto the property and off of it a few times).
The preserve was located in Morongo Valley and was a nice detour for a few hours. It was free but did accept donations. Bring water. Even in winter, it was very dry and warm. I could imagine it being very hot during the middle of the day in summer, so plan accordingly.