You’ll typically find sand in the canyons, mostly in dry creek beds, not so much on any hills. One place that comes to mind is in Malibu Creek State Park. You can take a route through the creek instead of the fire road, and then add in as many hills as you’d like.
When we trained for the Lost Coast Trail, we actually just loaded up our backpacks and headed to Santa Monica. We got some weird looks hiking along the beach like that, but it did the trick (sans the hills, of course).