This trail is a about 5 miles.
There is several ways to get to the gazebo from here. 
This is probably the easiest way to get there. There are little obstacles like water/mud (in the winter months). 
There is also a Bridge that you can try and get you horse to walk over. (Bonita Valley Horsemen put it in on there annual Trail Trials a couple of years ago.)
This trail has Great Views of Sweetwater Reservoir). The Gazebo has a Picnic table and 4 polls to tie up your kids/pony’s. 
This is a good practice trail to go on. Not that long and not really hard except for the hills/rocks/cactus. :)