Last three years I've gone in May, 2nd week, for my BDay. All I can remember is that they have been my best trips ever (going solo, always better with DSis!)
I don't remember bad crowds? I rode everything I wanted to and then some. I had FP+ I didn't use! I do EMH/RD and stay late whenever possible. I go back to the resort mid day. I park hop. I walk-up TS for all lunch meals.
There were no long lines without FP+ that I can remember, particularly later at night. I use my FP+ around dinnertime., then get FP+4 etc. or standby.
Love May weather, usually quite hot, possibly 1 hour of rain that I can remember!