Thanks for all the information everyone! Good to heard that beaumont could produce nuts in 8ft tall. I think Dana White seem to be the popular one. I still have to research on which kind I should grow.
As for squirrel get to the nuts. I'm thinking of growing macadamia nut at my front yard, so it could serve as ornamental tree. When the tree get big enough to produce nuts, then I will figure out how to protect it. I have a couple options I guess, like putting a bunch of catnip around the nut tree so the neighbor's feral cats (8+ cats!!!) will some how guard the tree. Worse case is the squirrels will get to the nuts and leave my mango, lychee and longan alone.
But so far I have seen less than 2 squirrel since I move in to my area 2.5 years ago. There are more peafowls than squirrels!