seems like baldwin hills (to the south) and griffith park (to the north) might be your best nearby gravel bets. some definite hills/grades but fairly, immediate payoff vs
santa monica mountains/san gabriel mountains 3+ mile ascents everywhere you look along with the drop-off/pick-up inconvenience. if you're in town for a spell, there's more recommendations but if in town for 5 days or less, keeping it close is probably best. griffith park will be your classic la vibe and sights and easier to extend ride length.