Curt, the "Cliff's Notes" of all this is that there are basically two spots in town that are the highest traffic spots if you just plain want to see trains. Both spots offer anywhere between 60-100 moves in any given day. Some are locals and some are mainline pass throughs. You will see everything from BNSF z-trains to coal trains to run-of-the-mill manifests. You're bound to see a complete locomotive roster between the 3 railroads. Those two spots are Dayton's Bluff (aka Hoffman), and University Ave NE in Minneapolis. You will see the BNSF, CP, and UP all pass these spots and are pretty much guaranteed trains if you are concerned about traffic. Given your limited time (and gas prices) these are no brainers. I can't disagree with the other spots you've considered, but if you want to see action with limited downtime, don't stray from these two hotspots.
As for your trip to Thief River Falls: the BNSF Staples Sub (Northtown Yard in Minneapolis to Fargo, ND) and a part of the northern transcon literally hugs US Hwy 10 virtually the entire stretch. The tracks parallel Hwy 10 in many spots. The aformentioned spots near Coon Rapids and Elk River offer the outer metro area scenic spots as well.
Like Braham said, there's a good chance some of us will be out railfanning then anyway, and would be happy to give you a tour.
-Nat
