I don't know when they go on sale, but I doubt you are going to need them.
I recently went to Universal on a Monday in late-August. Before I went, I debated getting a FOTL pass -- it being summer and all -- but now I am so glad I didn't spend the money.
I had very little trouble with lines all day. The Mummy and Jurassic Park, for example, had wait times of maybe 10 minutes all morning long. Even in the afternoon, I saw times posted on the info board of 25 minutes for each. (The busiest ride that day, with afternoon wait times of 45-50 minutes, was Back to the Future, because it was closing the following week. But I had walked on that at park opening.)
There were also minimal waits for most of the shows. I actually just walked in to Special Effects, Waterworld and Animal Actors shortly before they began (and got great seats for all). The only reason I ended up waiting for Backdraft, Terminator and Shrek was because I had just missed their start times. A FOTL pass wouldn't have made any difference in those cases.
The longest wait I had all day was about 45 minutes for the Studio Tour (noon-ish). My only complaint is that the sign at the top of the hill said the Tour had a 20-minute wait time, when in fact it was double that. But other than that, it was smooth sailing.
