Adobe has recently released a new version of Photoshop Express 3.1. New version allows you to print your photos to your nearest Walgreens directly from Express.
In the Home page, Tap on "Order Prints" button and select image source (Camera Roll or Adobe Revel). Select the photos and "Print to Walgreens".
Pick your prints from the nearest Walgreens store.
Correct me if I am wrong but it looks like the app was just updated on 4/29 and the order prints option is no longer in the app
Order prints is there in the latest version (only for iPhone) 3.3