I was at Disneyland Monday from about noon until 4. I can verify that Disneyland and Downtown Disney was not built for heavy rain (didn't visit DCA). the water doesn't drain very well, big puddles everywhere. my shoes were soaked within a few feet of leaving the restaurant where we had lunch. at the Downtown Disney parking lot the water at the curbs was almost up to the sidewalk. the sidewalk handicap ramps were completely flooded.
one other thing that I noticed. the design of the new monorail windows did not account for rain. there is no water seal at the top of the window when the half slider is closed.