Firstly is this an hoa that would prevent you screwing to the concrete (I can’t tell if we are talking outside or inside). How big are they? Are they framed? A French cleat always works but you’d have to have someone screw it to the concrete. Liquid nails works in some situations

We use Alien Tape as seen on TV. Holds a lot of stuff up. Four one inch pieces should hold an acrylic mirror assuming the frame is also lightweight. It does not come off but you can peel it off. You can buy Alien Tape in stores.

There's also Command hooks if the mirror has hanging wire. They have sizes for different weights so use the weight of the mirror as a guide. Again all general stores carry them. Use a piece of Alien Tape to secure the bottom of the frames to the wall.

Thanks for the like. I don't know if Command hooks work in the rain. Alien Tape will work in the rain for sure.