Typically CA does not have the same high humidity that FL does. I usually do WDW for spring break and find it to be sticky, humid even then. CA does not usually have the same, it is more of a dry heat. We were at DL earlier this month and I wore capris and a light jacket at night. It was about 80 during the day and probably dipped into the low 60's during the night.
You are not going to freeze to death without a jacket though and I continued wearing my flip flops during most of the evening. Although my DS did get wet on the Grizzly River Run one night and forgot his jacket, so I had to buy him a sweatshirt because he was cold (think he did it on purpose)! But I would definately pack a light jacket, sweater or sweatshirt. You won't need anything heavy, but it can get somewhat chilly feeling when the sun goes down, esp. if the wind is blowing.