If you can negotiate the convoy of Maclaren strollers and typical Chestnut Street lunch crowds, you'll be treated to some great sandwiches and salads at Blue Barn. That tuna sandwich is quite tasty, and their salads are generously portioned. The staff is quite friendly as well. Best to call ahead and place your order in advance.
2105 Chestnut St (between Mallorca Way & Pierce St) (415) 441-3232