Tarragona!
I hope I'm not too late to rescue you from a horrible holiday choice. I stayed two weeks in Salou two years ago and it was AWFUL. It's package holiday territory and you'll never return to Europe if you go there and imagine it's typical. It's like, for example, Kissimee in the Orlando area of Florida - only worse.
Tarragona is a lovely ancient town with a Roman amphitheatre where st Paul once preached and lots of other interesting historical associations AND there are beaches nearby. There's also Port Aventura a short trip along the coast in the direction of Salou - a Universal Studios type park with rollercoasters and stuff.
Barcelona is less than an hour away on the safe, clean, quick train and you could take the bus from Tarragona bus station to Mont Blanc, a pretty little town in the hills.
And you can always take the train to Salou for a day at the beach and see all the people turning boiled lobster pink and drinking too much lager, and give thanks you chose Tarragona.