Windows Phones still don't have orientation lock in Tango, but I remedied this situation a while ago. In case you need enlightenment, read up on this post.

The new version has some bug fixes and optimizations, as well as the ability to pin a secondary tile to the start screen. The secondary tile acts as a quick toggle between the orientation locked and orientation unlocked states. Tap on it, and the application will fire up for about half a second, then close and take you back to start. This makes it just a little easier to toggle your orientation lock, for people who are tile junkies. I heard this idea requested a few times, so I thought I'd cook it in with my extra time today.

Download it here, and be sure to give me feedback in the comments. Thanks!