AC blower blows on high and all speeds but there is very little air flow through AC vents what would cause this?

a bad switch.. it probably works on very very low... wiggle it and see if you get a momentary gust of air.. if so .. nothing 80 dollars wont fix.

blocked heater or evaporator core. Fan may have sucked up something and blown it against. Blend door or one of the others in an automatic temp control may be causing the air to not flow properly.