guppies are pretty hardy, but whenever doing a fishy cycle one should monitor ammonia and nitrite levels and do water changes to keep those levels below 0.25 ppm preferably.
Are you in the North or South Bay? In the South Bay, my favorites were always The Fish Tank in Sunnyvale, and Dolphin Pet Village. I didn't list those in the LFS thread because I haven't lived in the Bay for ten years, and am not sure if those shops are still good.
The Fish Tank was awesome, too. Smaller and more intimate than Dolphin. Everyone who worked there was VERY knowledgable and as a kid it was my ambition to one day work there It was always my very favorite store. I hardly ever remember any sick or dead fish in their tanks.