My son is in the Marine in San Diego and the car is his even though it's registered to me because I bought it for him. My son has the car in San Diego and the emission inspection is due soon. Can the emission inspection done out there in San Diego?

I believe because he is in the marines and not in his state of record he can get a pass until he changes his state of record or leaves the military I could be wrong though. This is more a question to pose to the MTA's dmv

Yes

Different states have different emissions standards. You should call the office to get your options.