If my parents are out of town, does my grandmother or stepfather become the next legal guardian?

Mom and dad divorced since I was 1, now 15. Both mom and dad are out of town. My grandmother lives nearby (10 min walk) and my mother is leaving me with my stepfather, but I'd much rather be with my grandmother. Being the dramatic person my mother is, she's saying my poor old grandmother can't handle having me over and it would be too stressful for her. Of course, all my grandmother wants is to spend some time with her only grandchild, and she's healthy and active as opposed to what my mother says. Now the question is, my mother, who has legal custody while she's gone, is leaving me with my stepfather, but I'd rather be with my grandmother. Do I have the legal right to refuse to be with my stepfather, and be with my grandmother, another one of my legal guardians?