Summer is coming and its getting very humid, and I was thinking of putting a duct from my AC to my comp. Not into the intake fan but through the mesh grills where the opticals would be. Would I have to worry about anything, like condensation?
Depends on how good your AC is. Most chuck out too much moisture, which will lead to condensation. Plus, as the case cools and the air outside remains humid, condensation will form.
Either way, your idea will only work if one: your case is at least moderately insulated to retain the benifit of the cold air, and two: you find some way of directing that cold air towards the components that need it (namely your chip and graphics card(s)). Just cooling the air in the case down doesn't do too much.
A better alternative would be to use your AC as a cooler for a water-cooling system. If you're close enough to your AC unit, that would help. If not, you can setup some coils in the AC vent.