The surrounding area of Salou is a sightseers paradise. Whether you go on trips organized by your tour operator, or hire a car, there's plenty to see. The tourist office have lots of information on interesting things to see, all within an hour or so's drive. There is beautiful mountain scenery, with castles and monasteries galore. The monastery of Poblet is one of the finest, as is Escornalbou (very steep drive though). The entrance fee for the majority of these buildings is only a few euros.
The area to the North -West of Salou, is a huge vine growing region, often, the vineyards themselves run guided trips down into the cellars where you can watch the wine making process, this is usually free.
If you are an aquatic bird lover, then take a trip down to the Ebro Delta National Park, an easy straight drive with main roads all the way.
A lovely place for a picnic is Sama Park, which is a couple of miles North of Cambrils, 14 hectares of fruit trees and winding pathways. The peacocks wander freely and you can investigate strange cavelike structures built from limestone in 1881.
If you are more of a city lover, Barcelona is only 100 km away, get a good map, driving in this city is not for the faint hearted! Tarragona, only a short drive (or bus trip), has a big shopping centre on it´s outskirts called Central Park, with everything from a supermarket, to designer clothes. The centre of Tarragona is worth a vist too, loads of cafés, bars and a lovely cathedral.
Reus, also a short drive (or bus trip), is easy to explore on foot. Follow the route advised by the tourist office, which takes you past impressive modernistic architecture, or wander around the cobbled streets of the city centre. There are plenty of Tapas bars where you can try small portions of Spanish cuisine. If you like shopping for clothes and shoes, this is the place for you.
Unless in a hurry, avoid road tolls by driving on the National roads. You will save money and see more.