Grocery shopping near Union Square... there is a Safeway down in the financial district north of Embarcadero Center, and if you go South of Market there is a Trader Joes and a Whole Foods. I'm sure there are also numerous smaller local markets. There's a Cala Foods on California and Hyde, as well.
As far as dining, well there are many, many restaurants of every kind and every budget. Pick up a copy of the San Francisco Zagat's.
Maybe it's because I have lived in the city for eight years, but one of the parts of town I actually AVOID is the Haight-Ashbury. It is crowded, dirty, overtouristed, and overrated. There are many MANY other neighborhoods in SF that offer fantastic shopping and food without the drawbacks of Haight St. Just my opinion.