If you go south on Saturday, you need to leave the
Disneyland area by 10:00 (and earlier is better!), otherwise you run into a lot of traffic on I5 with lots of other people going south to San Diego or Mexico for the weekend. If you go back to Orange County from San Diego on Sunday afternoon you can run into the same kind of thing, though I don't really know how bad it is these days. It used to be you had to leave San Diego by noon, otherwise don't bother leaving until 7:00, but I don't know if it's still like that.