You can only purchase them a month in advance as they only set the price based on the anticipated crowds.
If your date is further than one month in the future, it won't 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 click "Go." It should then take you to a page that has the Universal and Islands of Adventure Express plus pass along with tickets.
Try it with a date in 2 weeks and you will be able to see it. Right now it will only show that option if you are going before March 26.
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.
Are you referring to the Bonus pass which is pay the 2 day price, get 5 ( for admission to parks) or the Express (Front of the line booklet) bonus pass?
Are you referring to the Bonus pass which is pay the 2 day price, get 5 ( for admission to parks) or the Express (Front of the line booklet) bonus pass?