Hi Bissari,
It is in fact easier to exchange US $ than Euros on the parallel market, sometimes reffered to as "black" market. US $ are just more widely accepted. If exchanging in Merida try local tour operators or posadas, they may be able to help. As for some good posadas, Casa Sol, as mentioned above is very nice, but you may also want to look into La Montaña, Mucurisa or Mama Tila, all of standard accomodation. Plenty more abound such as Jama Chia and Posada Patty, both of budget accomodation. Prices for the activities you are interested in vary according to the type of activity and its location. I also recommend visiting the Llanos from Merida, a great destination thriving with wildlife. Mind you it is easier to see a giant anaconda in the dry season than it is in the rainy season, since in the dry season water levels drop and these amazing reptiles are slightly more exposed.
As for Morrocoy, on the way there you may want to stop off in Coro to enjoy its small but quaint old historical quarters, visit the Medanos de Coro (sandunes located to the north of the town) and its surrounding beaches and national parks. In Morrocoy there is a very nice posada located on a hillside in the National Park itself, close to the town of Tucacas, thereby giving you a great view of the keys that conform the Morrrocoy National Park. It is quite pricey but you get all your meals included as well as boat trips to different keys. On the cheaper side you can venture into the town of either Chichiriviche or Tucacas for some cheaper posadas. Camping is no longer allowed in the Morrocoy National Park. Occassionally, the govenrment will allow for people to camp on a couple of "Cayos" (keys), but at present this is not the case. You wold probably find it a bit tricky exchanging money in Morrocoy, besides you don't want to be wasting your time doing so, so my advice is to get it exchanged beforehand, for example in Merida where you will probably get a much better rate anyway. Boat owners are reliable, but do not pay them beforehand, negotiate the price, especially if you are very foreign looking, since they will most definitely want to overcharge you. Different keys have different prices. The price also varies according to whether you share the boat with other people or hire the boat for yourselves. I was there last weekend with family and friends, we had a boat to ourselves and we paid BsF 360 to go to Playuela, very nice key but gets somewhat crowded at weekends and very crowded on public Holidays, and to Playa Azul, a slightly more distant key also somewhat crowded at weekends and very crowded on public Holidays.
Puerto Colombia in the Henri Pittier National Park, is definitley worhwhile visiting, there are some amazing beaches surrounding the town, which are only accesible by boat, my favourite being Tuja. The cloud forest is also a great spot for adventure. You can go trekking into the Amazing Henry Pittier National Park, birdwatching, since the park is home to a great variety of birds and even canoping just outside Puerto Colombia.
Hope you find this info useful.
Travel safe,
All the best,
Thomas
Caracas
berry_venezuela@hotmail.com