Universal usually only sets the price based on the anticipated crowds so sometimes you can only purchase them a month in advance, so if your date is further than one month in the future, it might not show the express pass plus option when you purchase the tickets.
Go to:
http://www.univacations.com/
Click on "tickets only" then enter your dates and number in party. Then
click search.
When it takes you to the next page. scroll down to where it says:
"Departure Date: Nights: Use the GO button to Book Your Tickets Now!"
Enter the date and number of nights and click "Go." It should then take
you to a page that has the Universal and Islands of Adventure Express
plus pass along with tickets.
That says: Option Price Guide
Universal Express Plus-Islands of Adventure $XX.xx (this will be the
price not x)
Universal Express Plus-Universal Studios Florida $XX.xx
Included features and/or taxes:
Handling Fee 2.00
Do NOT purchase express unless you know the exact date you need them as
they are dated and only good for the date on the pass. Also the express
pass plus is sold for each park. You can't use the Universal express pass
card at IOA. They do have one that includes both parks and is about $10 more.
