The beach is nice, beach views from the 2 main bedrooms and living room are pretty. There were a total of 4 bedrooms, 3 baths on Casa Mermaid. We used the charcoal grill as well, it was hard to find starter logs in any store in the Penasco area. This house is 25 mins away from the city, you do have to drive through some unpaved roads dirt roads to get to the house, but the beach front is worth it and the house is pretty as well.
The backyard patio provides plenty of shade and chairs to sit, listening to the gentle waves. Tide changes quite a bit, which is cool to observe, water is very shallow by the beach and nice and warm. It was nice to see pelicans and seagulls hanging at the beach. There are some seaweeds in some areas of the beach / sea (minimal though), but that didn't bother any of us. I was able to walk right over it. Swimming in the warm water was a blast for all of us, including our 11 yr old.
Finding the house the first time was a challenge as Google doesn't understand Mexican house addresses. Once we got there, we dropped a Pin on Google Maps, then it was easy to get directions every time using our dropped Pin.
The main grocery store is the Bodega Aurrera (next to Sam's Club), but it's limited in what you can get from there. Most of the activities happen in town (Puerto Penasco), we enjoyed walking in the Malecon, parking at the $5 location at the Malecon. Street vendors do constantly ask you to buy their stuff, just keep walking. Plenty of restaurants by the beach, and local souvenir shops at the Malecon.
Before leaving, we did get our auto insurance (from AZ to Penasco), had a 25 - 35 minute wait (due to the line of cars) each way at the Border, passports were required to show only when reentering the US again. No paperwork is required for heading to Mexico.