Five of us stayed here for ten days for a post exams holiday and had a great time. The apartment was comfortable, the staff were friendly and the location was great.
But if you are booking a three bedroom apartment, be warned! We were very lucky to have gotten one of the few apartments at Ontario that have three separate bedrooms. Many of the others that are booked out to people expecting a 3-bed are actually 2-bed apartments with a futon in the living room. This may not be a problem, but if it is, I advise you to specifically ask for an end room, as from what I can gather these are the larger apartments.
The only other drawback to Ontario is the live entertainment downstairs. Maybe its a matter of taste, but I personally found the incessant bingo, quizzes etc hard to stomach after the first few days. In our case the matter was made worse my the fact that our apartment overlooked the entertainment area, so the amps felt particularly loud from where we were.
I wouldn't let you this put you off Ontario though, the location is great ( walking distance from La Pineda and regular buses to Salou from a bus stop round the corner) so its easy to get out during the day. My only word of advise is that if your going clubbing, remember that clubs are generally open until around 6am, and the earblasting entertainment at Ontario, starts around 9.30am, so sleep can be hard to comeby:P.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.