My husband and I stayed at the RIU from June 1-7, and have absolutely no complaints about the RIU. Our room was perfect with no problems. I would mention that the shower floor was about 4" higher than the bathroom floor so it was always a little tricky stepping from the tub to the tile floor, but really who cares! Maid service came promptly every day, and the toilet, shower, AC etc. all worked great.
I've read a lot of complaints about the unswimmable beach. Actually, most of Cabo is unswimmable. The RIU actually has a prime location. The other 5 star resorts also have unswimmable beaches (i.e. Solomar). They call Medano beach swimmable, but it's a little roped off area with hundreds of people and surf. If you're looking for Carribean-type beaches with calm turquoise waters, go East. The Pacific is not it. It's a fishing area with significant surf around the entire Peninsula. If you love to swim in the Ocean, I would highly recommend the RIU Palace in Playacar outside of Cancun.
As for the "partiers" around the pool bars, what would you expect? In fact, the RIU did an excellent job of separating the main pools from the bar pool area. The somewhat murky water at 4:00p.m. in the bar with floating limes and straws does not mix with the main pool. Also, it keeps children out of the bar area completely. Frankly, we met some very nice and interesting people at the pool bar which made our vacation that much more memorable. If you're not into meeting new people over a cocktail (or seven) than just stay near the main pool, you can still get drink service.
The activities staff at the RIU did an outstanding job. My husband did the shooting, the Boccie, the pool volleyball, etc. and had a blast. It's up to you how much you want to get involved but if you like that sort of thing, it's there.
My best advice is to leave the resort and explore the downtown at least a few times during your stay. Cabo is a safe and friendly town and a $10 taxi ride or long beach walk away. The food at RIU is typical all-inclusive. There's plenty to eat, and it's hit and miss. It also gets a little old day after day. We ate at many of the local restaurants. I highly recommend Lorenzillos if you are a lobster lover. It is expensive, and you need a reservation. We never got sick, and I ate and drank everything!! I also recommend the Office on the beach for lunch if you're a people watcher. It is full of people of all ages and types. It is heavy on the vendors, but they learn quickly if you continue to say "No Gracias". The food is also quite good, at least the Mexican food, and the Margaritas are strong.
The only reason I did not give the resort 5 stars is that it wasn't quite as nice as RIU Playacar. However, I think this is because the beaches are so much nicer in the Carribean waters than on the West Coast. Overall, the RIU is a nice clean resort, a great location, and an excellent value. Plese feel free to email any questions.