Nebraska is a no brainer. Hotels are cheap unless you are right near the stadium on game day.
Flights to Detroit and LA are not that different. Seeing spirit into detroit for $150. Even if it is a few bucks more than LA, once you factor in hotel, game tickets, etc, it's not that much compared to the overall cost of the trip. There will be lots of reasons to go to LA as a BYU fan, not so many to go to Ann Arbor or Lincoln.
I'd rank them
1) Nebraska
2) Michigan
3) UCLA
That is also my personal order of likelihood of winning.
Why not 2?