Any suggestions?  We're thinking of a trip in August.  

This is an older post, so not sure if you're still interested in responses, but we have been traveling to Rocky Point (Puerto Penasco) for almost 30 years.  Opinions may differ, but my wife and I prefer Sandy Beach.  It has very nice sand, and because the beach is so flat, the tide goes out more than 100 yards.  It's a very good for walking or running. 

Lots of places to stay (rental condos).  The "Sonoran" properties are very nice, with ocean views.  The Penasco del Sol is also nice. We camp at Playa Bonita RV resort, right on the beach.   Its a very relaxed atmosphere, but also family oriented.  So if you're looking for a semi-nude or nude beach, you're going to need to be either be discreet, or creative.  Using the condo balcony, for example, is a good option, but beaches and pools will have kids and grandkids running around. 

The area is not super developed, so there are some resorts and housing developments outside of town that are remote, and may offer the seclusion you're looking for, but you'll need to drive there, maybe on an ATV.  (Many places to rent those in town.)  Hope this helps.  The beaches are great.