Should I just till the soil and plant them? Or mix in manure and compost first?

I live just south of Orlando and hope to plant an avocado, blueberries, peach, mango, and banana.

I have no idea on mango.

For the banana amend it with everything you have, the richer the better and water water water.

The blueberries are different. You don't want to put them in our native soil at ALL. They need very acid soil so mix together pine bark fines (2 cf purple bag labeled pine bark at walmart) and Canadian peat. Mix the two 50/50 and use an entire purple bag and equivalent peat per plant. Make a hole half as deep as the root ball but 3 feet across and dispose of the native sand. Fill the hole up with the pine fines peat mix and plant the blueberry into that so that each plant looks like a little mound. Mulch with more pinebark fines and add sulfur to the surrounding soil. Only use acidic type fertilizer on the BB bushes such as Miracle grow camellia and azalea formula and never use a fertilizer that contains muriate of potash.

Just be prepared to protect them in winter since they don't like frost/freeze...but I'm sure you already know this :o)
Enjoy your fruit trees and good luck!