Normally I eat afterwards but I am only going 15 miles. When I go on longer weekend rides I definitely eat before. You can get by for short distances (less than 1 hr) with just last night's dinner and some water, but longer time on the bike needs fuel. If you figure it takes two ours to digest even simple foods, a pre-ride breakfast for a short ride isn't going to do much. It is important to eat after a ride to replace fuel used though.