I want to make a fruit crumble and bake it at my friend's house...how long could I safely leave the unbaked crumble at room temp.?

If it is a true crumble it should only have fruit thickener flour sugar and butter. If you are worried just put the crumble part in the fridge and just before you want to bake it crumble it over the top and bake. But really there isn't anything in it, although I don't know your recipe, that should go bad. I am guessing this is a Gourmet Recipe for Two?