I know you ruled out Uptown, but Roat Osha's patio kicks ass. It's not directly on Hennepin so you don't get hassled by people, but you're only like 15' away so you still can watch the circus of street traffic. Just take side streets to get there and you won't have to worry about the detours. I'll be there later tonight.
Leaning Tower of Pizza has an awesome sidewalk patio, and they have happy hour from 10:30pm - 12:30am. You'll have to get there early though if you want a spot, as seating is pretty limited.
I'll second Suzi's and Black Forest. And Vic's too for that matter.
It really depends what you are in the mood for and if you are just having some drinks or planning on eating. But here's a few of our favorites
-My wife and I love grabbing a pitcher of Sangria and eating some tapas at Solera. Is it as good as when Tim was running it? No. But if you stick to the traditional classics, it's a big leap above most bar food options.
-We also enjoy the Aster Cafe/Vic's patios. Nothing beats the river, the skyline views, and the stone arch bridge. It's usually quieter there too so we can have an adult conversation.
-We all can use a tiki drink or two in our lives and the patio at Psycho Suzi's is fantastic with it's river views.
-In Saint Paul, we often enjoy W.A. Frost for a nice bottle of wine and relaxation amidst the bustle of the city.