Which Riu? The one is Los Cabos? Never been to a wedding there, but I did go there for a family trip over the summer 2013.
Here are some things to expect:
-BIGGEST THING!!! The place is separated into two sections; the Riu Santa Fe and the Riu Palace. The Santa Fe is the "cheaper" section of the hotel, where myself, FH, his brother, sister-in-law and two of their friends stayed. The Palace is the more expensive of the two, but still located on the same property; FH's parents and sister, brother-in-law and their baby stayed there, because they had read it was a quieter area than the Santa Fe, AKA less drunk 20-somethings running around blacked out during the day/more luxurious rooms. If you are staying at the Palace you are able to use the Santa Fe's pools, restaurants, entertainment, etc. You cannot switch sides if you are at the Santa Fe. Our biggest problem (so annoying that we all ended up moving over to the Palace after the second night) is that the place is HUGE and using the in-room phones to call from one section to the other was faulty at best, so finding each other was a nightmare. FH and I felt like we spent the majority of the day trying to hunt down the Palace side people and hoping they wandered over to the Santa Fe area, because we were not allowed over to the other side. It was weird. Like I said we ended up switching and FHs dad managed to get the switch discounted, so it only cost the two of us $65 more. If you do decide on Riu, make sure everyone goes for the Palace section to save on frustration. It's a bit more expensive, but the overall stress completely disappeared once we moved areas and made it sooooo much more enjoyable.
-The food in general while not bad was mehh. Mostly buffets which felt like they'd been out too long by around 4pm. However, go to the sushi place. Was great! Very fresh and tasty! Nothing bad to say there. Italian place is neither here nor there; generally good, but no five star accomplishment. Stay away from the steak house. I'm a western girl, so I love medium-rare and rare steak, but thing was barely cooked. The gal who ordered a well done got a steak rarer than mine, so it was basically still mooing when it came out.
-Good resort if you have little ones. Very child friendly, if that's something you're looking for. They has a ton of activities for the older kids and were very accommodating with our niece and her parents (she was just over a year). They provided a playpen for a bed and always had highchairs. Though, one of the housekeepers did give mom a fright when she picked her up in the hallway. The customs on childcare are different there. Just a cultural thing and nothing came of it one way or another.
-Decent night life. They have a club and there's a ton of young people ready to dance and party on the Santa Fe.
-Drinks, delicious, but totally watered down. I'd say you'd have to down 2-3 for every one you would regularly. Though when you're drinking in the sun all day, this may not be a huge deal.
-Staff's English in general was not as good as other places we've stayed at (Dreams Resorts, respectively), though they are incredibly nice and do try their best and hey, you are heading to a different language speaking country, so not totally shocking.
-Beds are not super comfortable even in the more expensive rooms. FHs parents got a suite and the thing was also like a stone.
These seem fairly negative responses, but over all the place was a decent vacation and the Riu staff are dolls.