Here is a little list of some cultivars that are good dwarfs. The ones with a "*" I would recommend for taste after doing a good deal of research.

Carrie *
Julie *
Ice cream
Cogshall
Fairchild *
Lancetilla
Rosigold
Neelum
Pickering *
Mallika

I happen to be a big Fairchild fan myself. Great taste, super productive/fungus resistant, pretty small growth habit. The fruit don't have much color but the flavor is what counts.

I have most of the trees that Nullzero mentions as dwarf mango trees. My personal choice if limited to one small mango tree would be either a Fairchild or a Pickering tree. They both taste excellent will stay small and do very well healthwise. I would not recomend planting either Julie or Ice Cream as your only mamgo tree, lots of care issues and usually not a lot of fruit in Florida.