The drawback of using Walmart is that if you DO have to put on chains to get up and over a pass, you will be stuck with them afterward. We used to rent chains by the day from random gas stations near the snow-line, once we became aware that a chain restriction had been imposed.
I assume you'll be going only to Yosemite Valley, from the west through Merced, Mariposa and El Portal. If so, treat yourself to a delicious lunch at Marie's Mexican Kitchen
(used to be Sinaloa) in Merced on the way home...great enchiladas and guacamole tostadas!