I was born in San Diego and lived there until I was 9.
Then I was raised in LA MESA from age 9 until I left at 18.
Lived all over San Diego before moving back to LA MESA at age 30.
Finished raising my children in LA MESA. It is urban without being big city.
Did not leave LA MESA again until age 38 when I moved to the Hillcrest region of San Diego and, after 5 years there, I moved to Little Italy in San Diego.
Less than 6 months after that I was visiting my new boyfriend when we had the Northridge Earthquake, January 17, 1994!

Ended up living THERE and in Burbank, CA.
In 2001 we moved to Wrightwood, CA, 6000 feet up in the San Gabriel Mountains, 90 minutes from Los Angeles and 120-180 minutes to San Diego.
My parents still live in LA MESA so I am still there for a few days almost every month.
A nephew of mine and his new wife (in their late 20's) also live in LA MESA and they love it there.
Jamul IS very rural, out in the boondocks... great if you have horses.
I don't know about current Santee, but...
I would move back to LA MESA or GRANITE HILLS if I ever come back to San Diego.
Mt. Helix is very PRICEY and most of the homes are older now.
ALL OF SAN DIEGO is pricey, but now is the time to bring your Canadian dollars down and buy with our foreclosure crises.
I think you will love San Diego and I wish you all the luck in the world there!
I might move back again sometime in my life, but am very happy right where I am here and now.
GOOD LUCK!!!