looked through a list of hotels in the area that you specified. found 2 with good rates and centrally located. close to market street, powell street cable car line, s.f shopping center and union square where you will be within short walking distance of macy's,the cheesecake factory and tiffany's, and my favorite, The Virgin Megastore. (It's a record company, not the other thing)

Allison Hotel at Union Sq. $49 per night
417 stockton st. 800-628-6456 ask for airline rate.

Hilton Towers S.F. $75 per night
333 o'farrell st. 415-771-1400 ask for airline discount.