Is suntan lotion a homogeneous mixture?

Yes, suntan lotion is a homogeneous mixture. All of the ingredients are evenly distributed throughout the lotion. If you took a sample from the top of the bottle it would be the same as a sample that you took from the bottom of the bottle, or any other place in the bottle.

On a molecular level, suntan lotion is a mixture of many different ingredients, so it is heterogeneous in composition.