June/July is the best for Mt Hood I believe.  I am a newbie too and climbed with TMG in late June.  They are all fantastic guides.  We got to meet several different guides during our training and outfitting.  ( I did the climb with the American Lung Association)  and every single one of them was professional, experienced and a pleasure to climb with.  I cannot say enough nice things about them.  Good luck to you, Mt Hood is incredible !