[MENTION=141750]PDXPremier[/MENTION] - Short answer - no, you don't end up airside.
Long answer - when you and at STS, you walk off the tarmac to a TURNSTILE, which dumps you landside / near baggage claim. You will then need to go back through security, which only operates before a flight takes off (they close the gate into the security area between flights). Not much to do in the landside (or airside) areas. There's a cafe landside, and a statute of snoopy. I would probably just stay onboard.