To me, the best spot to a proper introduction to the ocean is HMB, roosevelt beach, during the spring (northwest wind).
For many reasons:
it's side onshore like waddell, not straight onshore like OB.
It usually is smaller than waddell.
The beach is long, so you can rig up away from anybody else, less traffic.
It's not as popular as waddell, so again, less traffic.
Now for the cons:
it's more of a shore pound break, but on a small day, it's pretty easy to pass, also, if something goes wrong in the waves, well, you're right next to shore.
There is a reason HMB is less popular than waddell: beside the fact that you need to pay $5 for parking, you don't get that many days at HMB. The fog that kicks in at the end of spring shuts down the place, when waddell still get clearings.
Now waddell on a small day is great, but, the beach is smaller, and as a result, a lot of traffic happens in the impact zone. Now you could ride downwind but you would end up in the rip and if something goes wrong, well, good luck swimming back.
Ob is a fantastic spot and one of my favorite.
BUT: waves don't break clean, so it takes a while to be able to "read" them.
The wind is onshore: as a result, a lot of people stay inside and you have a HUGE amount of traffic (try to picture 3rd ave at the upper launch in front of the cove on a weekend but instead of having water downwind of you you have sand and waves breaking upwind of you).
Also, I've noticed beginners tend to keep their kites parked when something goes wrong or to crash it. Again: two bad reflexes at OB.
If you crash it, you only have a few seconds before putting it back in the air before a wave takes it and drag you along with it (hold your breath, everything is gonna be fine).
If you keep it parked and don't move it when you fall in the water: the waves will push you toward your kite, put slacks in the lines and the kite will fall from the sky (then it crashes in the waves, see above).
Now don't get me wrong, waddell and OB are fantastic spots and they blow a lot more often than HMB.
If I had to pick an order of preference for where to bring a friend for his/her first time in the ocean (as long as (s)he is a independent rider, knows how to ride upwind all the time, self rescue, body drag to the board, etc...) then it would be:
1)HMB
2)Waddell
3)OB
Now remember, I'm talking about northwest wind during this whole post.
South stormy wind are a whole different story...
Again, this is just my opinion and I'm sure other riders will be more than happy to talk about this.
Oh, and for any beginners reading this: don't go by yourself out there. keep it safe!