We had a wonderful tour guide named Roy who was very knowledgable and had a large lens so we could see things up close and even take photos through the lens. We saw sloths, monkeys, birds, iguanas, raccoons and had a great walk on the beac too! It was worth every penny!

Take the bus from Quepos until it dead ends. Honestly, you won't need a tour guide (the ones that hassle you at the final bus stop). If you are okay with walking about 1/2 mile or so from the bus stop to the actual park entrance, you'll do fine. Pay your entrance fee. The walk to the beach is quite a walk. So soak up the scenery.
It sounds cliché but the beach is like a post card. Even better are the hikes on the trails off the main trail to the main beach where all the raccoons/monkeys and such attempt to steal your food. I blame the tourists. I recommend going on one of the side trails that will take you to the top (almost a mile or around 1400m) where you will have the most picturesque view of the beach. It can be treacherous so ¡caudate!. I literally gasped, I wasn't expecting it. I saw a group of monkeys near me that didn't mind me at all. Another trail from the main road leads you to a more secluded beach that is almost your own (at least during low season). There are bathrooms to change/rinse into a bathing suit (only near the main beach/trail) if you so desire. No soap/shampoos allowed.

Having an experienced and knowleageable guide is integral going through this park. We were fortunate to have Manuel Cabalceta as our guide (www.manuelstours.com). While walking down the main path without the trained eye of our guide, we would have easily missed many interesting species - including various plants, lizards and birds. Manuel has been studying for many years and shared his vast knowleadge and experience with us. Unfortunately, with all wildlife it is quite unpredictable what you will see on any given day. We saw a sloth, jesus christ lizard, racoon and various small birds. There is a lot that I feel we missed though, but was not the fault of our guide.

There is a peaceful & gorgeous beach inside of the park, but we did not know to plan for that so didn't bring our swimsuits/beach gear with us. I would definitely plan to spend some time on this beach since you are already in the park. It is much nicer than the public beach nearby.

It was very nice, we saw white faced monkeys, two sloths and squirrel monkeys. The beach was very relaxing, enjoyed swimming and hiking though the park.