Where is a good destination for an August vacation?

My boyfriend and I (we are in our mid and late 20s) are looking to travel somewhere with nice beaches, rainforests and waterfalls. We like to hike and sight-see and never mind an adventure! We are willing to look at places in the Caribbean (even with hurricane season). We also enjoy the nightlife (but are not party animals) so we are not looking for somewhere very secluded and quiet. Our price range is about 2000 and are hoping to find good deals at this time of the year.