I think the dinner was in LA. He did meet with some at Miramar where he gave a speech after touring the border wall prototypes. Pendleton is between those spots and folks from there could have also easily traveled to MCAS Miramar.
Maybe Marine reserve activation requires meeting in person for security reasons. Apparently the only thing deep state fears and didn’t game out/prepare for was getting their asses drug into a plumbing van by a team of jarheads. Semper Fi!