The latitude of the spaceport depends on where you are going. If you are going to the moon or any of the planets, close to the equator is good. If you are going to the ISS, then somewhere around 45 degrees N latitude is better. The latitude of the launch facility should match the inclination of the orbit of the spacestation. If you are just looking to throw things into low orbit for a bit (space tourism), then it doesn't really matters where you put your spaceport.
ISS was launched into an inclined orbit that was half-way between Cape Kennedy in Florida and the Baukinor (sp?) facility used by Russia.
Long-Term, if we are going to have spaceports that support lunar or interplanetary missions, the spaceport should be located at or near the equator and with ocean to the East. This would allow the spacecraft to take advantage of the Earth's rotation to get into space. For Polar orbits, it is better to have Ocean to the West, since you are trying to kill all your rotational speed.
Ocean is good so that anything that falls off or is separated, will fall into ocean and not on people. SSTO (Single-State-To-Orbit) craft would have less need for the ocean stuff, but it might still be desired to reduce noise over populated areas. The noise thing is part of the reason New Mexico was selected by VirginGalactic for it's spaceport, that and the high and dry climate.
(Scientist mode OFF)