Yes, active duty get in for free with your military ID, family receives 10% off.
"Dependents, aged 10 and over, must present valid dependent ID. The San Diego Zoo and San Diego Zoo Safari Park offer a complimentary one-day pass to the Zoo and an Africa Tram Safari at the Safari Park throughout the year for active duty military, cadets of military academies and reserves with active orders." - San Diego Zoo website. They also offer 10% off for spouses.
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