'Costa Adeje', in the south of the Island (literally translated as Adeje Coast) covers a very large area - Playa de las Americas, Puerto Colon, Torviscas, Fanabe and practically everything inbetween!
In short, there is LOADS to do in or around Costa Adeje, but I guess that isn't really as informational as you'd like, so here goes.
If you're looking for places to eat in Costa Adeje, there is a wealth of restaurants available, serving a massively varied selection of different foods, from English through to typical Canarian and Indian! More information on places to eat in Costa Adeje here: http://www.tenerifedining.com/restaurants/locations-south/adeje.php
For places to visit in or near Costa Adeje, again, there are plenty of things to pass your days out :) Probably the most fun (in my opinion anyway) is Siam Park (waterpark), which holds several records, one of which is the record for the largest man made Wave Machine in Europe! Theres loads of slides and rides there, as well as the mentioned wave machine, which is crazy fun :) More information here: http://www.siampark.net/en/
Alternatively, you can't go wrong with the Monkey Zoo Park (although this is a little out of the way - just a little further than Los Cristianos). It's a zoo where you can actually walk through the cages, with the Monkeys, and feed them. It's a fun day out for anyone of any age. More information on this zoo here: http://www.destinationtenerife.com/excursions/animal-parks/monkey-zoo-park.php
If it's simply bars and clubs you're after, you won't be dissapointed there either. As with any holiday resort, there is a dizzying array of bars, both normal and themed, so you'll certainly find something to your liking. Las Americas actually does nightlife like nowhere else, so if it's that kind of night out you want, then Veronicas is certainly the place to visit. Holding several of the most well known clucbs in one location (Tramps, Bobbys/Busbys), you really cannot go wrong.
If you're looking for a more 'refined' night out, head further into Las Americas, near the Safari shopping centre, and visit the Magic Bar and Buddha Bar to name but two. Both of these have live music/DJ's of a more refined type, leading to a more relaxed night out. I highly reccomend popping up to Biancos on the first floor of the shopping centre either for food or just cocktails. The cocktails there are out of this world ;)
My own experiences