East of Jacumba is the Yuha Basin.
A great place to go for beginner trails would be in the Yuha Basin just off the 98 or south of Dunway staging. There are dozens of trail that criss cross the area with some good sights.
Lots of dirt trails with hills and rough areas to get your suspensioin all crossed up and provide lots of practice for wheel placement. Some rocks but they are relatively small (1-2 foot) along some trails and you can choose to run over them or go around them. Lots of loose sand and the main wash is suitable for fast runs. You will have to work at breaking something but will find enough challenges and enough areas that you can make challenging by taking the "right" line to get some real benfit out of it.
The fossil shell beds are a big thrill for kids and are pretty amazing for adults too. All kinds of beuatiful selenite crystals, multi colored lavas, obsidian, wilmite, jasper and even some pertified wood north of the main wash. If you like to such things the basin is good place to search in.
There is very little traffic in the basin unlike areas up the S-2 or superstition that is overrun with folks 24-7. Nice thing about Yuha is the border patrol runs the main wash every 3-6 hours and at worst its a 3 mile walk to the 98 or I-8 if you need some assistance.
BLM has marked every trail and intersection clearly. BLM has maps both at Dunway Staging and at the Hwy 98 entrances. They are also available at the BLM office in El Centro.
John