This is such an awesome place to visit, and I really feel the need to spout about it to everyone I meet.
It's located just outside Guaza, and you can reach it by heading down the TF1, past Los Cristianos (and heading towards Santa Cruz) until you hit the turn off for Guaza. Take that turn off, and then follow the road round under the TF1, keep going straight (so don't make the mistake we made all those years back when we first tried to find it and end up back on the TF1, going back from where we came :P), and take your first left. Follow that road all the way along, don't turn off at the Cactus Park (waste of time imo, but hey, thats where it is if you're interested), and keep going till you see the car park for the Monkey Zoo.
Prices are 10€ per adult, 5€ per child, and they are open from 10am till 6pm, but last entry is at 5pm. They sell bags of food (highly reccomended) for 3€ a bag. We end up buying 3 or 4 per trip
You can follow the path through the zoo, and enter into a few of the monkeys cages, and hand feed them, always very enjoyable, not too busy, and a lot of fun.
Theyve recently finished work on another walk-through cage, with yellow pawed monkeys in, and the rest of the park is filled with various species of monkeys (inclding a Drill, which is a fearsome sight), guinea pigs(?), leopards, and a few birds.
It's always a fun day out, and theres some pictures below.
I also made a short (2 minute) video of our last visit, which you can
see here - if the link doesn't take you to the correct place on the page, just scroll down about halfway.
Hopefully theres no issue with posting the link (it's family friendly, honest!) here, if so, pm me, or let me know and I'll remove it.
Heres a few photos (all taken by me from various visits - I also have more, if you would like to see them, post in here or pm me).
'Bear' monkeys! 
Hungry turtles :P 
Knock knock! 
Relaxing.