Coca Beach is very nice, and the beach front is clean (something that isn't always the case with Daytona, for example).
Not sure what you mean by which beaches? Simply take the 528 to Cocoa Beach and choose whichever area looks best to you. There are public parking places (free) and beach areas that have changing buildings and public restrooms. You may want to look for one of those areas over a simple pull over (beach access from a public roadway).