> I'm wondering if it's legal to obscure your license plate
No, not only can you not act to conceal them, you have a positive obligation to actively keep them readable. See, California Vehicle Code Section 5201(a): "License plates [...] shall be maintained in a condition so as to be clearly legible. [...]"
No, not only can you not act to conceal them, you have a positive obligation to actively keep them readable. See, California Vehicle Code Section 5201(a): "License plates [...] shall be maintained in a condition so as to be clearly legible. [...]"