Answer: I would be very patient in allowing the plants time to come back into growth, however I would be concerned about trying to keep hydrangeas alive and healthy over the winter in a pot. If they died back too far into the stems over the winter they may not bloom this year.
Hydrangeas (I am assuming you have the H. macrophylla type) should not be pruned in the spring except to remove any stems that are well and truly dead due to winterkill. The flowers form on the previous year's growth, so pruning in spring removes flower buds. If you need to prune, do it right after they bloom.
These plants are susceptible to winter damage and need to be kept in a sheltered location out of wind and protected if possible from the coldest exposures.
Generally an eastern exposure is satisfactory, or a bright location with dappled light all day. A western exposure, with that hot afternoon sun combined with the moisture stress of growing in a container, would very likely be too stressful on the plants and so you would see them wilt every afternoon in the heat of the summer.
I'm sorry I can't be more encouraging. If you really liked the look of the hydrangeas last year, perhaps you could replace them each summer and consider them as annuals.
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