Avocado trees grow wild here and the fruit is free for the picking. I know where many good tasting trees are located and when they produce. I have an extending fruit picking basket/pole that rides in the back of my pickup. Otherwise you have to fight the mongooses for them (mongooses LOVE avocados). You can find ripe avocados here year-round if you know where to look.
Avocados do not produce seeds that are the same as the fruit they come from. The seeds are almost certainly cross-breeds. If you have a tree that produces fruit you like the best thing to do is air-layer.
Mangos are the same way here, except they fruit May - September.
I haven't bought avocados or mangos in over seven years, but I eat them all of the time.
I make an awesome avocado - tomato - Japanese cucumber - sweet oinion - salad... with olive oil, sea salt, and coarse-ground black pepper..