For Spanish, I believe that you can start anytime (if you have a little Spanish). Go along and ask, whist there perhaps you could offer exchange classes with the students learning english. You have to ask the secretaria permission to stick a notice up but generally is’t not a problem.
I don’t know personally any of the language schools in Vigo. Here in A Coru?a lots of the private language academies offer spanish for foreigners aswell as english for Spaniards. Don’t be put off by the fact that nothing will be in English in class - it works well just in Spanish.
Get youself a good spanish-english dictionary and I’d suggest a Spanish secondary school dictionary aswell. In the spanish part of the spanish-english, study the part on pronunciation, spanish is phonetic, so once you learn the basic sounds you speak as you read (unlike english). Practice reading, pronunciation and comprehension by buying a newspaper every day - El Faro de Vigo or La Voz de Galicia would be my recommendations.
When I arrived in Spain for the first time I arrived in March, without knowing anything in Spanish. I signed up in the EOI in April at the basic level - the course finished in June, but it was a start. I signed up for the same entry level course in September aswell, because I had missed the first 7 months of the course. In September, before the start of the EOI course, I signed myself up for a one week intensive total immersion course in Santander. This included four hours in the morning, four in the afternoon, lunch with the teacher in a restaurant in town and lodgings with a Spanish family. It was 10 years ago now, and wasn’t very cheap. I didn’t come away from that being able to speak Spanish, but my understanding was much much better: once I came back to A Coru?a I found that I could follow my Spanish friends’ conversations much more easily. I?m sure that this one week intensive course was worth doing, when I did it; I had studied somthing of the basics: SER & ESTAR, regular verb construction in present, perfect and future tense. Probably taking the intensive course before having these basics would have been a waste of money.
Good luck with it.