Not sure if they will. They do have a special where you can buy online directly from Universal and get a bonus 2nd day there. The catch is that you have to activate it at Universal before using it anywhere else. They also have fees for their online orders.
Hello,
Sorry for the delay in responding, but we checked with our Universal contacts and unfortunately it is not possible right now to upgrade to a 2-day pass or a season pass. Hope that helps!
Disneyland will give you a $250 credit for an adult and a $235 credit for youth ages 3-9 towards the upgrade of your choice (at the current gate price). Hope that info helps.
I have the City Pass and didn't know you could add days on. We would like to go to the Zoo, what would we need to do to add that on? Nevermind, I found the answer to my own question here: http://www.citypass.com/southern-california/san-diego-zoo
It says you can only get them at citypass.com
Which in fact means it will work out cheaper for me to buy my Zoo ticket separately because I got my CityPass at a cheaper rate through Costco.