Sounds like you will be in CA. Publix wins hands down in the US. But they are only in the south east. CA grocery stores very greatly in quality even within chains. Your best bet is to visit each place around and pick the one your like the best.

I was partial to Ralph's when I lived in CA but only because the store near me was really fancy. There were other Ralph's I'd not let my dog visit. Trader Joes is a love it or hate it place as is Whole Foods (I hate TJ but think WF is fine their competitor The Fresh Market I love). Targets are hit and miss with groceries (Super Targets have them regular Targets have limited selection if that). Don't bother going to State Bros. if there is one near your hotel 95% of them suck. Vons like Ralph's has some upmarket locations and some real losers. Albertsons is kind of mediocre all around which sometimes makes it the winner unfortunately. Food 4 Less can be pretty awful (there were always flies at the one near my apartment). Don't discount Walmart. Sometimes a brand new Walmart can be a fine place to shop but the CA grocers unions may have kept them out of the grocery business in CA (that was a hot debate when I last lived there).

I'd visit each to check them out. You might also ask at the front desk which in the area are the nicest (perhaps ask for the top 3 nicest and then visit each). Good luck. I hours your find a place you like.