Looks like I've been able to help myself on this one. I'll post this
here b/c others had asked about this in prior emails and I never saw
an answer given.
You can make your own custom legend by keeping the return values from
each plot command:
l1 = plot(<y1's stuff>)
l2 = plot(<y2's stuff>)
legend([l1,l2],['y1s tag','y2s tag'])
works like a charm.