regular outdoor ply is an acceptable substitute for marine ply if money is tight. it's made with the same waterproof adhesive, but the veneers are lower grade, whereas marine plywood uses top grade, with no knots or voids. be sure to paint the wood with the paint of your choice. many people choose epoxy resin, or else 'spar urethane' for a clear coat. but any outdoor grade paint will work fine, if occasionally repainted.
pressure treated woods do not tend to play well with aluminum boats. the chemicals used to keep the wood from rotting when in contact with the ground are metallic in nature, and these metals will tend to cause the aluminum to corrode. the same chemistry behind the sacrificial zinc anode on your motor. except the aluminum hull is now the sacrificial anode. not recommended.
hope that helps.
cheers,
Brian