Dreams and the japenese restaurant are the dressier restaurants so plan your nicer outfits for those nights. The other are more casual and the buffet anything goes. If that helps. Some people did get really really dressed up, I don't know if it was for a special occasion or what.
I would wait until closer to your trip to decide about the malaria meds, you only need to start them one week before your trip so youv'e got some time to see how it is then. I was also at sunscape week of 3/6 and saw very few mosquitos 6 or less but it only takes one infected bite so take that for what its worth. Take lots of singles with you for tipping, not that it is necessary but you will find while you are there that you will want to give to them. We didn't go tip crazy but gave a fair share in both money and gifts and really got a good response from it and it was nice to know we put a smile on someones face.
Unless you get a swim out room, I would not want a room on the 1st floor cause on a few occasions we did see things creeping under doorways on the ground level floor hallways (ie palmeto bugs and geckos) we were on the 2nd floor and didn't see anything in the halls or our room.
Sun is very strong there, I tan easily and my sholders and chest burned and I switched to using my kids spf 50 sunscreen My fair skinned husband burned with spf 30 on the 1st day and spent the remainder of the week in the shade. So take a higher spf sunscreen and apply often, you don't want to waste any of your vacation in sunburn pain.
One more general tip is to take mostly small bills for purchase ($1-$5
-$10) you plan on making especially when bartering(sp?) cause you can't tell them you will only pay $10 for something and pull out a $20. and this way we never rec'd any peso back for change either. US dollars are commonly accepted.
STB is a beautifly resort, I'm sure you will enjoy and if you decide you don't want to go, I will gladly go in your place :)