i just finished my visit in Puerto Madryn and the area (December).
there are many ways to travel in the area - renting a car, taking a bus, or taking a tour - they are different by the prices and the things you get to see. Peninsula Valdez is the main attraction of the area. the reserve is very big, and you need drive a lot (about 6 hours) in order to see little, wether you take a tour or rent a car. if you want to see the whole reserve you have the to take into consideration 2 things:
1 - the animals are very far, and its not like you see in the pictures. so you don`t really get to see them very well. for me the main attraction was the whales (yes, you get to see them also in Dececember, when the weather is good). other then that i saw very little and from very far.
2 - prices - the cheapest price i found for a tour is 150 pesos. pay attention that the prices for the tours dont include the entrance to the park - 40 pesos more (190 total). if you rent a car with 3 more people (4 in a car) and want to go to the the peninsula by yourself, the whole day can cost you about 125 pesos + 40 pesos for the entrance ( 165 total). of course, this price is correct only if you don`t drive more then 400 kilometers, which is limit of the rental agencies. if you want to drive more then 400 kilometers (and see all the reserve ) - you have to pay more... other then that, you will see only parts of the reserve.
i recommend to go only to the whale watch in Peninsula Valdez. the boat tours to see the whales leave from Punta Piramide, which is very close to the entrance of the reserve, and you can take a bus there from Puerto Madryn (12 pesos to each direction).
the lowest price of the tour boat is 60 pesos, only if you make a reservation from Puerto Madryn a day before (if you buy the ticket inside the reserve it will cost at least 80 pesos).
this way, your day in the peninsula will cost 124 pesos in total and yo