livelovelife

The closest place to go from the RIU to go out would be Coco (or Playas del Coco*). It is no more than 10-15 minutes from the RIU. I'm sure you could get a taxi or a shuttle there. The nice thing about Coco is that they have a main strip of restaurants / shops / bars so it is quite easy to navigate through the city on foot once you get dropped off by a cab. I'd probably say thats your best bet to go out and not go too far away. Another option that usually has quite a bit going on is Tamarindo. Its a nice busy beach town with tons of people and bars / clubs. Tamarindo is probably more like to 45 minutes - 1 hour away from the RIU so distance-wise, Coco would probably be your best bet.

To be honest, Septembers in Guanacaste change from year to year. Typically there is going to be rain. If you are lucky, it may not rain or it might rain earlier in the day and clear up by the time you would have your ceremony. The nice thing about this is that many times it will give a really great sunset. Unfortunately the rainy season can be unpredictable and you just never know. Either way it will be a beautiful day because it's your special day and that is all that matters!