For nighttime I would wear jeans and at least bring a light weight jacket. Having lived in So Cal all my live I can tell you that no matter how warm (or hot) it gets during the day, our nights are definitely cooler (and damper). That being said, if you wear shorts the whole time you probably won't freeze, but I'm just more comfortable in long pants (and sleeves) during the evening.
The 10 day forecast for Anaheim shows a range from 72-88 for the highs and 49-56 for the lows. Also, beware of the early mornings. The other day (Fri) we had fog/mist for most of the morning. Didn't wear off 'til late a.m. Can be very chilly.