Lotusland is awesome! Really a cool place.
(Goleta) "Beard's Tropics" a.k.a Norman Beard's awesome farm, HUGE selection of tropical fruit tree's in ground and in greenhouse, including a fruiting in-ground rollinia, tons of full size cherimoya tree's, and tons of cultivars of finger limes, peaches, nectarines, and more.
(Fullerton) Fullerton arboretum is a radical place with a very large selection of tree's, including ton's of garcinia's, a huge ice cream bean tree with a 50 foot canopy, finger lime's, in ground jackfruit trees, and TON'S more.
(Goleta) Terra Sol is a cool local nursery that also has an awesome tropical fruit collection, especially in the private section in the back, they have Mangosteen's, Jaboticaba's, and a bunch of Inga species in the back. (Find Clare and tell her that you know me, and she will probably let you in the back.)
(San Diego) Ong's nursery is a tropical fruit lover's paradise, hundreds, if not thousands of species crammed into a little slice of paradise. Quite pricey though! THey have tons of fruiting specimens of Starfruit, countless Eugenia's, Syzygium's, ANnona's, and Artocarpus. Even if you don't buy anything it is still really awesome. The people who own the place are very kind too and will let you try ripened fruit off of trees.
etc…
There are a lot more, in my experience the above are some of my favorites though.