SoCal weather is perfect all year around pretty much. But it will be warmer at Universal Studios since it is in "the valley" The only time SoCal weather isn't sunny and 75-80 is in January-Feb when you get rain once in a while.
Disneyland and universal are about 40 miles apart. Are you renting a car?
BTW IMHO, Universal is a one (
maybe2) day park. If you like rollorcoasters, Magic mountian (six flags) is just north of Universal. Knotts Berry farm is real close to disneyland, but not worth the admission if you ask me.
I lived there for 4 years and know alot about the area, let me know if you have any questions.