GSA kicked off its 2010 expo today in sunny — and muggy — Orlando. Today was devoted solely to training sessions as the vendors set up to display their wares and stragglers continue to arrive. This year’s event is well attended, with an estimated 6,000 feds and 3,000 exhibitors, similar to last year’s numbers. Tomorrow the main event, the floor show, opens up and the expo really gets going in earnest. GSA Administrator Martha Johnson officially opened the festivities a little after 4 p.m., saying that this year’s expo and those in future years will focus on sustainability. There are…