I am in fairly good shape, is it reasonable to to the trail in 2 days or I need at least 3?
Hiking from the trailhead to May Lake is about an hour. Hiking to Ten Lakes basin from there is a full day of hiking. Depends on when you actually start hiking as to how far you are going to get. I think it would be hard to start later in the morning and get to Ten Lakes Basin in one day from the May Lake trailhead.
What's the best way to return back to your car at the end?
Hike back to where you started. That's really your only option.
And also what is the water situation on the trail?
You will find water in most of the creek and all the lakes. You should bring some way to purify you water: tablets, a filter, etc.
Any suggestions on a good place to camp for the nights?
Both May Lake and Ten Lakes Basin have plenty of places where people have clearly camped before. You should use one of those.
Any suggestions and tips are more than welcome.
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