House of Bread or Gus's for Sandwiches in SLO?
Guss' is a huge college-age scene. Muzio's downtown on Monterey is much more relaxed and the food a higher quality, I think. Giant Grinder owners are a delight, and the food is very good, though limited outdoor seating on a busy street. High Street has very limited seating, good sandwiches.
Muzio's is my favorite--and a great 1890's atmosphere.
We enjoy many varied sandwich places in SLO. The Giant Grinder is excellent on Broad Street, Gus's is very popular and very good and you specify your choices.
House of Bread is getting ready to move to new quarters at Marsh & Higuera,
I'd wait a while. High Street Deli is another good option.