My dad and I are flying from YVR on AC to SFO and have about an 8 hour layover. We then board a flight on Air New Zealand to AKL.

Will we be able to have our luggage checked all the way through, leave SFO and have lunch with family in town, and return to SFO hours before our flight (including going through security again)?

Our family member said we may not be able to leave the airport once we land. But that's not something I've ever tried.