I thought it could be cleaned up too, especially since the whole city area is sold as "exclusive".

No, it is clearly marked as no boats of any kind allowed.

As you pass the shops on your left of the little strip mall, all the big hotels are on your right. Cabo Azul, the Mayan is the last one you pass before the roundabout. Go straight, no turns at the roundabout. The road does end at the last hotel there, I believe is a Holiday Inn. You can park there, the path runs up along side of the hotel and around into the Santuary. The last time I was there, the water was too high and covered the paths. It's a lovely walk early morning.

Depends on your definition of an easy walk. The estuary can be toured from the south-end Holiday Inn side or the north-end San Jose side, but the connection between these two ends is flooded, requiring a long detour between ends. We took a cab from the tourist corridor for the sole purpose of touring the estuary and were somewhat disappointed by the stench of standing water and the lack of wildlife. However, we saw a few birds and got to spend some time away from the Cabo/San Jose chaos, so we called it a "win." If you don't mind spending the day walking about 10K, you'll have a good day.

We went to the Estuary in October for the first time. The path looked fairly new and definitely walkable. I'm not sure if it was redone, but we walked from San Jose to the Estuary and back. It was nice.

I don't know....I don't recommend that type of footwear anywhere except for a public bathroom!

Not all the way up to the Holiday Inn Resort. You can access it from an access road off the sidewalk up from the hotel and then it runs all the way below town to the causeway.

South on the main road about 1/2 mile, you come to a roundabout. Holiday Inn is on the left from this point, and Barceló is 5th hotel on the right, on the ocean side of the road.