Tioga Pass generally opens around Memorial Day, but can be later if it's a big snow year. The camping up in Tuolumne opens later, and not sure when the store opens & water is available. If you had a filter you would be fine, lots of free-range water up there.
Other than that, it's a great time of year. Have fun!
(The "valley" in "valygrl" is Yosemite Valley - I used to spend a lot of time there)