I’d recommend Carmel Valley as well. We picked this area as we both work in the La Jolla area and wanted to have an easy/fast commute, but didn’t want to live in UTC. Little did we know at the time that Caltrans was building a bypass from Carmel Valley to Sorrento Valley. Before the bypass was done, the commute was a breeze, now the car is barely warmed up by the time you’re in La Jolla! I’d recommend if you’re renting, to pick something as close to the 5 as you can since traffic backs up on the 56 during the rush.
I’d recommend that you take a look at the traffic maps, or try your hand at driving the rush hour traffic to and from the community you are considering. Some areas seem nice (and they are) until you drive the commute each morning.
As a side note, the 5 freeway has alot of side roads that can act as alternate routes if there is an accident or particularly bad traffic, but the 15 does not have these, so in my opinion, the traffic can be somewhat worse on the 15.
