Answer: Yes it would be better to move them to a location with morning only sun. Hot sun all afternoon is very stressful on hydrangeas. It would be better to move them now than to wait. When you dig them up, take as much of the rootball as possible, keeping in mind they may have grown additional roots beyond the original root ball when you planted them. Replant immediately, and mulch. Then water as needed to keep the soil slightly moist, but not sopping wet/saturated.
I would suggest you consult with your local professionally trained nursery staff about what to use as replacements. There are many different shrubs you could use.
Good luck with the move!
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