All or great communities. You can't go wrong with any of them. Where you end up with likely depend on 1) your budget 2) the type of house you are looking for, and 3) your personal preferences.
Carmel Valley schools are award winning and exceptional. The others are not bad at all, but Carmel Valley is known for its schools. Houses are modern - the oldest in the neighborhood were built in the late 19809's. Family homes start in the mid to high $600's.
Encinitas tends to have more older homes. with a bit more of a yard. The newer home sections of Encinitas will cost you $700K and up.
Carlsbad is probably the most affordable of the neighborhoods. La Costa is older, and quite lovely. Home lots are larger and La Costa homes are affiliated with the Encinitas school district. North Carlsbad homes send their children to San Marcos schools.
If you want an award-winning school, Carmel Valley is it. But I recommend spending some time looking around when you get here. Determine which community you are most comfortable in, and where you find a home you like.
I would be delighted to assist you in any way possible. Feel free to contact me directly - I can send you listings, and show you around when you come to town.
Have a great day.