Thanks for reaching out. Let's stay in touch. What mangoes have you had success with in Santa Barabra?
I plant any mango seed that is from an exemplary store bought fruit (Kent, Tommy, Ataulfo, etc) and they do okay is all I can say. The Kents seem to be pretty slow compared to Florida mango types but durable to cold (I left many outside as seedlings and a few survived down to 26f).
Did the same thing last year with FL mangoes I had delivered to Oregon when visiting and one of them is almost 4' tall in just a year. This is what you want, I understand, and shows that this is the type of seedling to hold onto. Not all of my seedlings performed this way, even FL seeds.
I have about 4 seeds that have sprouted now from about 20 FL mangoes of various types, and another I gifted to another SB grower has that one popping up too (buttercream). It seems the "cream" varieties: coconut cream, buttercream are the fastest growers for me here. The large and vigorous seedling I have is Coconut Cream. I'd say it takes a year before you can say it was a good seedling or not and surviving a winter is a good step too. My plants need to be really hardy up here. 110F day in the summer and 26-30F in winter here or there. I did protect a lot of the stuff I have with frost cloth this year.