Good eats around Union Square
Chinese - Hunan Homes (622 Jackson) (simple but good -- not so touristy that no locals eat there, but not so authentic as to put off visitors)
Mexican - Colibri (Geary between Mason and Taylor) (not Tex-Mex style, but more what you'd find in Mexico -- although in a trendy atmosphere. Tableside prep of guacamole, also great small plates like chicken tinga tostadas)
Italian - Scala's (a more contemporary style, not red-sauce Italian-American)
Italian - Fino (624 Post St.) (more traditional Italian-American, with house-made pastas and veal dishes)
Pizza - Uncle Vito's (Bush and Powell) (basic American pizzeria)
A fun atmosphere can be found on Belden Lane, with 7 different restaurants (French, Italian, Spanish, American) (between Bush and Pine, Kearny and Montgomery)
Hope that helps!
Maybe these will help-
432 Powell St
230 California St.
Cortez - nice upscale bar and good food
Tunnel Top- 601 Bush Street -more divey neighborhood type of bar, good cocktails
Bar Drake - in the lobby of Sir Francis Drake Hotel-more classic, lobby swanky style, great cocktails in the on Powell St at Post, close to Scala's Bistro
Hidden Vine- Wine Bar
620 Post St