Rokinon or Vivitar 85mm f/1.4 Lens

I'm really hoping that I can buy a lens soon before my son's basketball game in Canada on Labor Day weekend. Since were on a tight budget after buying a property in the Philippines. I would love to have Nikon Telephoto AF Nikkor 85mm f/1.4D IF Autofocus Lens but it costs over a thousand dollars which I really can't afford! So I saw these Rokinon lenses at Overstock.com for only $250. My problem is it's Manual Focus which I don't think I know how to properly use it. I have read good reviews about it and it's making me want to click that add to cart button. Help!!!