I'm assuming that your hotel is already booked for Anaheim for a week...otherwise, I'd recommend that you stay overnight in San Diego and check out more of the atttractions there instead.
Disneyland is MASSIVELY overrated, unless you are bringing little kids who think dancing cartoon characters in fuzzy suits are cool. I think that only spending ONE day in Disneyland would be the best use of your time. The rides are mostly shut down...and quite frankly, are completely pussy compared to the rides at Six Flags Magic Mountain. If you're into rollercoasters, then you DEFINITELY want to ride up to Six Flags while you're down here. X, Goliath, and Riddler's Revenge are damn fun. It's a straight shot up I-5 to Valencia...depending on when you leave, it's probably a little bit over an hour. I haven't been to Universal Studios in a long time, but again -- I can't see spending more than one day there. The tour is interesting (I guess), and some of the rides and shows are cool, but it's a big money trap for tourists.
If you're going to be in Orange County, why not enjoy other parts of Southern California while you're here? Spend a day at one of the beach communities getting some sun and doing some shopping -- Laguna Beach and Newport Beach are both great for that kind of thing. If you're into baseball, catch an Angels game at Edison Field -- it's a beautiful park, and the Angels are doing very well this year. Check out some of the museums in downtown Los Angeles, perhaps. From Anaheim, most everything is 60-70 minutes away if you avoid rush hour.
As for San Diego: Sea World is OK, I guess, but the San Diego Zoo is the coolest thing down there. The Wild Animal Park is also great to see, and it's a little closer to Anaheim than Sea World is -- check out more info on the web and see if it's your kind of thing.