The South Korea attacker left Spurs for LAFC this week for a fee of over £20m - a record for MLS.
Son attended LAFC's 2-1 Leagues Cup win over Mexican side Tigres UANL on Tuesday.
He later told reporters: "It's a dream come true. LA - what a city.
"If I'm honest, it was not my first choice. But the first call I had with (LAFC co-president) John (Thorrington) after my season finished, he changed my mind, changed my heart, my brain.
"He showed me the destination where I should be. Now I'm here, I'm more than happy, I'm so excited."
In a club press release published earlier, Son was quoted as saying: "Los Angeles has such a rich history of champions, and I am here to help write the next chapter. I'm excited for this new challenge in MLS. I have come to LA to lift trophies and give everything for this club, this city, and its fans."