We were on Royal at the end of May and stopped off here on a Sunday morning.
The overall impression from most who got off the boat is that there is NOTHING to do in Vigo. It really was like a ghost town. Only one coffee shop and a tourist gift shop open!!
You should really consider taking a trip to Santiago de Compostella if you want to see something of interest. My parents have been and loved it for religious importance/ pilgrimage reasons.
From what I can remember it seemed slightly cheaper than the Princess tour price if you took one of the hawking taxis to Santiago from literally the bottom of the disembarkment steps in port. I just asked the driver and the figure of Euro 120,- 'plus tolls' was what I was quoted, but we declined and made the mistake of trying to find something of interest in Vigo. Even the local tourist office was closed!! Otherwise Vigo was dead with no signs of life. It was actually quite dirty with 'some party' happening the night before as empty bottles and beer cans were strewn all over.
We just made a one hour walk up to the castle and >ahem< admire the view.
We were back on the boat by lunch time.
Hope this helps and you make more of that port than we did.