That said, I did discover a new access point to the New Sewage Treatment Ponds - new to me, at least, and I haven't seen a mention of it anywhere.
Here's a map of the area, with a few landmarks:
View Puerto Peñasco birding in a larger map
To the northwest is Cholla Bay and Laguna del Mar golf course, and The Reef.
In town is the Harbor and Malecon (waterfront street), Playa de Oro and a few other spots.
East is the Sewage Treatment Plant and the Estero Morua.
The only spots I visited were Playa de Oro and the Treatment Plant (November 2010).
Playa de Oro is probably like many other beaches in the area. Steep and rocky, there aren't many places to access it unless you staying at one of the campgrounds. However, at the west end was an empty lot (Los Corrales painted on one wall) with an adjacent 7-story yellow building. You could probably get through there. The west end held the most birds anyway, as the beach ends in a rocky jumble that gulls and pelicans like. I saw 9 Surfbirds here one morning, and Black and Ruddy Turnstones.
Seawatching can be productive - I saw two Blue-footed Boobies one evening and a Snow Goose fly by on another and frigatebirds on several occasions. Wilson's, Semipalmated and Snowy Plovers, Sanderling, and Marbled Godwit made for interesting walks, and the amazing sunsets/sunrises were a bonus too:
I visited the New Sewage Treatment Ponds entirely by accident. I was there with a group from my church, partnering with Amor Ministries to build a small house for a family. If you'd like to learn more, contact me or follow the link. The house we built, as it turned out, was a few steps from the north pond of the sewage treatment facility.
Previous reports had indicated that the STP could be difficult to access - needing permission from the guard, canals cutting off access, etc. I suspect conditions here change without much notice.
I was able to scope the north pond easily, and walk dikes east, west and south. Hundreds of gulls, 8-9 frigatebirds, decent shorebirds - about the only thing missing were passerines and ducks (Mallards, shovelers and ruddy ducks only).
To get to the New Sewage Treatment Ponds from the north, I will use the corner of Fremont and Dominguez on the southeast side of town as a starting point - there's a Pemex station on the corner. Head north on Dominguez, going over the railroad tracks at 0.3 miles. At 1.2 miles from the Pemex, turn right (west) on Juan Aldama - there's a store called "Abarrotes Gisele" on the NE corner.
Juan Aldama is a sandy washboard of a road lined with houses. As you head west the houses will become progressively newer and less "house-like". At about 1.6 miles you'll see a sign for "Yonke Vega" - the junkyard.
The north berm of the STP is about 200 yards south of Juan Aldama at this point. The west end is raised quite a bit, sloping to ground level at the east end; access is probably easiest at the east for this reason. The junkyard is at the west end.
If you've looked at the satellite map by now, you're probably as confused as I was, as it looks like barren desert. Well, I checked, and the satellite photo was taken 11 Feb 2006. In the meantime, thousands of houses (I use the term loosely) have sprung up, often cobbled together from weathered pieces of plywood and black plastic.
In the background you can see the existing house that we replaced; they borrowed the plywood, so after they get moved in they will return it.
I was able to walk down into the ponds, as the water level was not high. To the east is a dike that runs south, with water on both sides; it dead ends at a canal after 100 yards but provides views of one of the southern ponds. Parts closer to the houses looked like a frequent playground for some of the neighborhood kids.
With the houses so close to the berm, you may attract some attention from the neighbors, but the kids I met were very friendly and curious.
And yes, we finished the house; this was for a family of 6:
References for further reading:
Finding Birds in Southeast Arizona, p232-239
A Bird-Finding Guide to Mexico, p56-58