http://www.agroforestry.co.uk/
Mi experiencia :
¡Lo de Caberadi , Ingegnoli y Baumaux no se sabe de que variedad son, lo de Flora Toskana según un experto Americano de Pacn son las mejores para un clima come el de Toscana- Italia central, no sé si para ti seria lo mismo, seguro que las Inglesas de Agroforerstry non son para climas ibéricos !

In California, there are two sources of pecan trees:

L. E. Cooke Company
26333 Road 140
Visalia, CA 93292
Phone: (800) 845-5193

Linwood Nursery
23979 Lake Road
La Grange, CA 95329
Phone: (209) 874-3088

L.E. Cooke offers lots of named cultivars but they're all cultivars developed in Oklahoma and Texas.

Linwood has a couple of cultivars that they THINK might be good for California.

Joe (in California; my family is from Sicily)

You don't mention your growing zone but since you appear to be on the coast and palm trees are happy in your area, I'm going to guess that you're at least in zone 10 (USDA). Pecan trees are happiest in zones 6-9 but can be grown in other areas as long as the summers are hot and there is plenty of moisture. Pecans are originally from the SE part of the US which has hot humid summers and high rainfall. They also require enough cold in the winter to go fully dormant.
You probably can grow pecans in your area but be prepared to water them heavily during the growing season, they are very thirsty plants.
Instead of purchasing a tree you could buy nuts of the variety you want and go about it that way. The seeds usually are very willing to sprout but may not have the characteristics you're looking for. Of course a rooted cutting will definitely give you the plant you prefer. Which variety of pecan do you want?