You shouldn't consume food if it is kept between 40-140 degrees F for more than 4 hours. This is known as the food "danger zone". So no, I wouldn't eat it. Get a little cooler and an ice pack and you'll be good to go.
Pack a cooler I do it all of the time. Put some seasonig in the mayou before you spread it on the bread. Wrap sandwich in a ziplock and than alluminum.