Went to Salou in 2009 for a week with a few lads, we stayed in the (now called) Medplaya Piramide Salou. It was under different management up to last year but I'd imagine it's still the same as when we were there.
Rooms are big, clean, air conditioned (believe me, you will need it!) and it's nice and quiet. Five minute stroll to the main street area and beach, which is where pretty much all of the pubs, bars and restaurants are located. Pool is quite good, there's a seperate children's pool and there were games organised most day in the main pool. Food was good, breakfast has the usual Irish/English breakfast as well as the more continental oriented breakfast option. We still ate out most days though.
Port Aventura theme park is a ten minute taxi trip from the hotel. If you're planning on visiting here, you'll need to take the entire day, there's a lot to do and it can be very busy. The water park next to it is also quite good. Plenty to do on the beach too - pedal boats, banana boats and jet skis (VERY expensive!) El Toro steakhouse along the front promenade is a must visit - they do an unbelievable steak and some damn good vegitarian options too!
Nightlife is good, plenty of bars with live music although if you're into clubbing it tends not to kick off until after midnight as clubs stay open until 6am.
See what alpharooms are quoting you for flights, then check with Ryanair and Aer Lingus to see what they're looking for. We booked flights directly with Ryanair and the hotel through alpharooms and it worked out quite a saving.