Yes, the distances in Argentina are not to be underestimated! I only stayed two days in the area, covering the Valdes Peninsula on the second day. On the first day I birded the Trelew Lagoons, the Dolavon farmland and Punta Tombo Nature Reserve. I definitely saw a lot more birds on this route, which may be an alternative to visiting the Valdes.
Trelew Lagoons: About an hour south of Puerto Madryn, these are a couple of large lagoons on the outskirts of Trelew. They can be accessed from the dirt track
here, a short distance from the roundabout. There is a good viewpoint
here. You can follow the track east to another larger lagoon, but unfortunately at the time it was too muddy for me. Species seen: Chilean Flamingo, White-tufted, Great & Silvery Grebe, various ducks, Red-gartred Coot, Spectacled Tyrant and various other commoner songbirds.
Dolavon: About 30kms west of Trelew, I had Burrowing Parrot a short distance outside of Dolavon on the main road through Dolavon from Ruta 25 (
here). There were a couple of ponds further along this track with a variety of ducks, while the farmland scrub held the commoner local passerines.
Punta Tombo: Nature REserve about 2 hours drive south of Trelew which holds the largest mainland colony of Magellanic Penguins. There is also a good chance of seeing the endemic Chubut Steamer Duck offshore. There is also a good selection of various passerines in the surrounding scrub. Good stopping points include
Dos Pozos and this wooded area
here. Best accessed by taking Ruta 3 south from Trelew and then taking this
new road to Ruta 1. From here the nature reserve is signposted. Note that the northern stretch of Ruta 1 is gravel, as is the access road to the nature reserve.