It's actually quite safe to park in SF with two exceptions:
- With anything visible that might contain a valuable. Any devices in the trunk should be in Airplane Mode. If you're a tourist, don't park by a tourist trap.
- Any model with an oft-stolen catalytic converter, esp. Prius.
SF itself has higher-than-average tourist density, so it's a burgling destination too. But it's possible to park for decades and never have your car broken into.