I've been to Rocky Point (Puerto Penasco) many many times, but never on a dive trip. I have been there on hundreds of "beach bum" trips and I also snorkeled in a few different areas of the bay.
Rocky Point does have some great beaches and a nice surf. But there is a wicked tidal current. Somebody told me that Rocky Point actually has the biggest tidal differences in the world (the area is sooooo shallow and sandy that the water literally moves hundreds of feet out during low tide).
In all honesty, there isn't much to see in Rocky Point anymore. The area was heavily overfished and much of the marine life is gone. I used to go there when I was younger (1970's) and the area was vastly different. You'll see a bunch of sand bars, sting rays and possibly some trigger fish, but not much else.
As the last post said, San Carlos is a popular dive destination for those in Arizona and a much better one than Rocky Point. The drive is a little further -- about 3 hours longer from Phoenix -- but it's well worth the trip if you want to dive.
So if you're only wanting to dive, San Carlos is probably a better bet. But if you just want to hang out on a nice beach with a beer in your hand, then by all means try Rocky Point!
Thx...Doug