If the blocks were a lot of work to piece, I would just leave them alone , quilt it up and explain to GD that some of the signatures may run when washed. You could embroider over the original signatures but the pen may run underneath when washed.
If they were simple blocks and you feel like the extra work, you could use a light box to trace the signatures (using the correct pen) onto new blocks. Why can't people just follow instructions? Bummer!