Take it you're near Tamarancho area / Golden Gate National Recreation Area? Totally understand about the lack of "flat clear ground" out there.
A tarp will work perfectly fine, all one really needs is enough space to fit a body, it doesn't matter as much like a tent where "flat ground" is imperative for a good pitch! (As long as drainage is good and there is no pooling!)
That's the beauty about tarps is the flexibility to place them just about anywhere one's imagination will allow one to do so.
The other option is using a bivy (which is great when stealth camping in the tall golden grass while keeping out the bugs, in this case ticks!)
Or combine the two together for more options and coverage!
Can also use trekking poles to set-up a tarp! Can also use MLD's carbon fiber tent poles, if not using trekking poles to do the same job!
For out on those windy hills, pitch that tarp low!!!
Hope this helps!