can you buy contact lenses in Barcelona with a US Prescription

As long as the optrician can understand the measures, which should be in European standards and units, then it should be fine.
There are lots of optricians: General Óptica, Multiópticas, Alain Affelou, El Corte Inglés Óptica 2000, L'òptica Universitària, and also local optricians...just look for óptica in Google Maps and you will find lots of them

Thanks Joan G

I do believe measurements are standardized so you should have the same "units" in the US than here in Europe, but again, as Joan points out, it's best to make sure. Send the measurements to your son and he can go to any optician an ensure they're the ones also used here.

Note that there are indeed dozens of opticians, from big chains to small independent ones. Ask your son to shop around because there's an ongoing commercial war -so to speak- among them and there are special deals all the time (ie. get your prescription glasses for X euros and a second pair for just one extra euro, etc). As I understand he's a university student (right?), there's one, mentioned above, l´Òptica Universitària (roughly translated as "The University Optician") whose main target is, precisely, the student population.

Thanks all.

Yes he was able to buy his prescription contacts from l´Òptica Universitària.

BTW, is Vueling is the only airlines with direct flights from Barcelona to Florence Italy? Ryanair flies non-stop to Bologna and Florence is about 60 minutes via train from Bologna.

What route would be the best, I am trying to help 5 kids figure their travel for a weekend getaway?

Yes, I believe so, only Vueling serves Florence directly from Barcelona.

Anyway, and excuse me meddling... he's a grown-up, isn't he? Let him take charge of these things. Nannying him isn't helpful. Tell him to get in the forum and ask :)))

Good Advice. I had told him about the forum. :-)