Yes! Highly, highly recommended. We kept going after we reached Valenca, stopped for lunch and a walkaround of Tui, then back over the bridge to Valenca, enjoying the walled hilltop town before spending the night there, which I highly recommend. Tui is crowded with walkers starting there.
The walk along the Minho the following day was pure joy. No other walkers, nice stops along the way, gorgeous views as you are always walking next to the river. It was, in our view, our most enjoyable day walking of any stages on the Portugues.
It's well marked. You start on the Portuguese side and then cross at the first bridge. Cool signs on both sides of the bridge which we simply had to take photos standing near.
And when you reach the waterfront in A Guarda, you feel like you are on the Amalfi Coast. It's that good.