Sakura
The short answer is "Yes, it is worth a try"
As for signs, every child is different in how or if they signal.
Your child used to sign very clearly to you in the past and hence is very likely to do so again with encouragement. Some babies never signal and their parents relay on timing to catch the wees.
I would recommend buying a small baby potty for your daughter to use...i.e. Baby Bjorn Little Potty
I would start by trying to catch an easy wee after your child wakes up from any sleep/nap, sit her on a potty for a couple of minutes. You are nearly a dead cert to catch a wee.
If she wees in her nappy, sit her straight on the potty and you'll often get a longer second wee in the potty.
If you think a poo is coming and most mums know, stick her on the potty. I find poo's come in three sections, so make sure she has finished before whisking her away from the potty.
I talk to my daughter on the potty and/or give her toys to play with and unless she is actively pooing (which takes ages) I don't leave her on the potty for longer than a minute or two.
You can also introduce cue sounds if you like. We use Psss for wee and Prrr for poo.