The level of snow depends on the amount dumped this winter. Even though the west side is getting a normal amount, the east side and the Mt Whitney trail is below normal. I expect you will be hitting snow, though, somewhere about Outpost Camp or Mirror Lake. Once it gets steady enough, you can put on the crampons and keep on.
Before you hit the snow, the trail is easy enough. People have had trouble in the dark finding the trail
descending the bare granite "nose" above and just south of Mirror Lake.
Here's a link to an online interactive map showing the area I am talking about.
Once you reach Trail Camp, you can find your way even if the trail is hidden by snow, as most tracks will be going in the right direction. It is the lower area, between Outpost and Trail Camp that reportedly have tracks going all over the place when there is snow.
Take a good printed map -- print out the map from the above link -- and if you really don't want to get lost, carry a gps unit with the track of the trail loaded into it. (I've had good luck creating tracks using the gmap4 website.) We can find you a good track/route to load if you want to use one.
As for wildlife: In May, there won't be any bears. They only bother people in the parking area near the trail head, when they set their daypack down and walk away. Bears swoop in, grab the pack, and run with it. But there are so few people in May, bears will not likely come in until later in the season. Keep your pack inside the closed car or in a bear locker, or else on your back. Bears won't bother you with the pack on your back.
Hiking alone in the dark in May -- you will be completely alone. Wildlife will be no bother
at all. Just a thought, if you want to hike and see a few others on the trail, Saturday or Sunday would be your best days. Don't worry about the Whitney trail permit lottery in May -- based on previous years, there are always plenty of permits in May.
Climbing Whitney as a "day hike" in May, with the snow conditions is a monumental task! You have the altitude issues, snow and icy trail to contend with, crampons weighing down your feet, and lack of conditioning since you are traveling for several weeks before you go. Be prepared to turn around if it gets to be too extreme. Your life is far more valuable than bagging a peak.
