I bet when he sees a McDonald's he knows its McDonald.. Always point to the "M".
"Sonic starts with an S.. do you see another S?" What is the S sound? What others things start with SSSS?" These are the things we would talk about while driving around doing errands..
Our daughter's name starts with the letter P and we sometimes call her "P".. she was always pointing that letter out too. Then she asked about the letter my name started with and I told her L, so she would be on the look out for "moms letter"... The A's were always important since our Last name and my husbands first name begin with A.. This is one way that we searched for letters practically every day to and from day care..
I also used to let her bring in the mail and see who they were addressed to based on the first name initials. She was our mailman..
We never just taught her. she just kind of picked it up, through curiosity and through everyday experiences,, Grocery store, riding in the car, looking at her books, looking at the newspaper.. Talking about "what everybody's first letter was"..
I did not even realize she could read until I purchased some BOB books and she read the entire first set to me in the car on the way home, I had to turn the car around and exchange them fr the second set..
Such an exciting time for your son! Have fun..