My driver's license expires on Sep 10, 2020, I have a passport so I don't need a CA Real ID. since the appts are 2-3 months out, can I go to the SLO DMV office and wait in line to take the test. DMV website does not appear to be user friendly.

Yes you can wait in line. Go early to avoid getting send home because DMV will stop letting people inside at 4:15 p.m. Wednesday is not good day to visit DMV.

I would make the appt. I remember reading a 60day extention for expirations. Cops understand.

The lines can be extremely long, stretching out to 4-5 hour long waits. The doors open at 7 am and close around 3 or 4, so there's a very limited window for getting in.