There is only one way how to go from Porto to spanish city Vigo.
You have to go by train from Porto – Campanha.
Your final destination is Vigo – Guixar.
The website of comboios de Portugal – CP.pt are very confusing and it’s very difficult find out something there. Here you have useful information:
Single: 11,05 Euro (younger than 25 years)
Return: 22,10 Euro (there is no discount for return)
Duration: 2:15 h (be careful – in Spain there is +1 hour time zone)
Timetable – schedule
We found very cheap accommodation on Airbnb.com for 17 Euro for 2 people.
On this portal are a lot offers for accommodation, if you use this registration promo code, you have 20 Euro discount for first use. – www.airbnb.cz/c/ondrav1
Another alternative is cheap hotel in Vigo. (With this link you will have 10% discount.)