The biometrics letter just arrived in the mail this morning! Woohoo!
It's scheduled for June 4th, so while I'm in Canada (but of course, lol). I'm going to attempt an early walk-in this Tuesday while I'm in the town where the center is (about an hour and a half away). Since South Dakota is a pretty dead state when it comes to immigrants, I'm sure I'll have no issues.
I'll update on Tuesday once I'm back on how it went. Wish me luck!