4+ months in the West

Thanks for all replies. I wonder if the difference of opinion has anything to do with some commenting on access roads rather than the campgrounds per se? Yesterday on the NPS site it said some campgrounds would not be open until June

California State Route 120 crosses the Sierras at 10,000 feet elevation from the east (US 395 at the town of Lee Vining) and enters Yosemite near the crest. It typically is closed (depending on snow pack) until around Memorial Day. Yosemite valley is open all year and can be accessed from the central valley of California. There are several routes across the Sierras that are kept open all winter, SR 120 is not one of them. You can cross the southern end of the Sierras and drive up the central valley or travel across near Reno and use IR 80, US 50, SR 88, or SR 70, all kept open all year.

The bigger issue with Yosemite will be the crowds. If you can go before school is out, you might find is a little less crowded.