Yes, valid. It is named rodalies (that is catalan-in the rest of ESpanan name is cercanias) and its just a normal 3-car electro set with hard plastc seats in grey/orange. You probably cannot miss it. NO REServations even possible. Makes a lot of stops, also along Costa Brava and runs about ev 2 hrs-in BCN in the ccitytunnel at amny stations-so Do check which is best for your final destination.
In Spain, you'll have to add a lot of trains manually because RENFE doesn't bother to share most of their timetables with the rest of the world. After adding a train manually to My Trip and then to My Pass, you should be able to display the barcode via My Pass > Show ticket and then everything is OK.
If this is your only journey on the day, then it's probably not worth using a travel day for. If I recall correctly, a normal ticket is around 10 EUR.