On Friday, the prince ordered a beer and burger at McP's Irish Pub & Grill in Coronado.
Victor Swircz and his fiancee Laurie were having their rehearsal dinner when they spotted Prince Harry eating nearby.
Swircz introduced himself to the prince and asked for a photo, but he declined, saying he was not allowed.
Instead, Prince Harry introduced the couple to his security guard, and then used Swircz's camera to take a photo of the couple with the guard.
He's in the U.S. for a two-month long helicopter training course.
The prince is among 20 students in the British Army participating in the training that ends at an Air Force station in Gila Bend, Arizona. They will take part in fire exercises.