It rained towards the end of our trip (just back tonight) but we did parks anyway. I brought cheap ponchos and we could have used the good Disney ones. Take them with you everywhere as these storms really do pop up! We entered Buzz Lightyear to clear skies and emerged to a monsoon!!
It was crowded to us. We usually go earlier in May and noticed bigger crowds. Go early, rest in the afternoons, go back (not to a EMH park!! Too crowded!!!) in the evenings.