Thanks soD -
In the case of my '94, you are correct that the VSS is on the transmission itself.
I didn't allow myself enough time to really dig into the issue this weekend. Best I could do was check the VSS connector at the tranny, as suggested by TomO. Looked pretty good actually; clean, no corrosion, good connection.
Also managed to find my Honda Service Manual which has some trouble-shooting steps if the speedo doesn't work... first step was to verify I'm getting the proper voltage to the VSS sensor itself when the ignition is on... which I am.
... was time to call it a night right after I did that... learned the hard way that leaving the ignition on overnight will kill the battery...
One thing I'm not sure how to resolve... since this is an intermittent issue; I'm not sure when I'm testing things out if it's in the "working" state or the "not working" state. Just jiggling things around to test things (like continuity) could put things into the "working" state. Guess it's just a matter of working my way through it...